| Message ID | 1407254732-8332-2-git-send-email-deathsimple@vodafone.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > From: Christian König <christian.koenig@amd.com> > > Avoid problems with writeback by limiting userptr to anonymous memory. > > v2: add commit and code comments I guess, i have not expressed myself clearly. This is bogus, you pretend you want to avoid writeback issue but you still allow userspace to map file backed pages (which by the way might be a regular bo object from another device for instance and that would be fun). So this patch is a no go and i would rather see that this userptr to be restricted to anon vma only no matter what. No flags here. Cheers, Jérôme > > Signed-off-by: Christian König <christian.koenig@amd.com> > --- > drivers/gpu/drm/radeon/radeon_gem.c | 3 ++- > drivers/gpu/drm/radeon/radeon_ttm.c | 10 ++++++++++ > include/uapi/drm/radeon_drm.h | 1 + > 3 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c > index 993ab22..032736b 100644 > --- a/drivers/gpu/drm/radeon/radeon_gem.c > +++ b/drivers/gpu/drm/radeon/radeon_gem.c > @@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data, > return -EACCES; > > /* reject unknown flag values */ > - if (args->flags & ~RADEON_GEM_USERPTR_READONLY) > + if (args->flags & ~(RADEON_GEM_USERPTR_READONLY | > + RADEON_GEM_USERPTR_ANONONLY)) > return -EINVAL; > > /* readonly pages not tested on older hardware */ > diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c > index 0109090..54eb7bc 100644 > --- a/drivers/gpu/drm/radeon/radeon_ttm.c > +++ b/drivers/gpu/drm/radeon/radeon_ttm.c > @@ -542,6 +542,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) > ttm->num_pages * PAGE_SIZE)) > return -EFAULT; > > + if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) { > + /* check that we only pin down anonymous memory > + to prevent problems with writeback */ > + unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE; > + struct vm_area_struct *vma; > + vma = find_vma(gtt->usermm, gtt->userptr); > + if (!vma || vma->vm_file || vma->vm_end < end) > + return -EPERM; > + } > + > do { > unsigned num_pages = ttm->num_pages - pinned; > uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE; > diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h > index 3a9f209..9720e1a 100644 > --- a/include/uapi/drm/radeon_drm.h > +++ b/include/uapi/drm/radeon_drm.h > @@ -816,6 +816,7 @@ struct drm_radeon_gem_create { > * perform any operation. > */ > #define RADEON_GEM_USERPTR_READONLY (1 << 0) > +#define RADEON_GEM_USERPTR_ANONONLY (1 << 1) > > struct drm_radeon_gem_userptr { > uint64_t addr; > -- > 1.9.1 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel
Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: >> From: Christian König <christian.koenig@amd.com> >> >> Avoid problems with writeback by limiting userptr to anonymous memory. >> >> v2: add commit and code comments > I guess, i have not expressed myself clearly. This is bogus, you pretend > you want to avoid writeback issue but you still allow userspace to map > file backed pages (which by the way might be a regular bo object from > another device for instance and that would be fun). > > So this patch is a no go and i would rather see that this userptr to > be restricted to anon vma only no matter what. No flags here. Mapping of non anonymous memory (e.g. everything get_user_pages won't fail with) is restricted to read only access by the GPU. I'm fine with making it a hard requirement for all mappings if you say it's a must have. Christian. > > Cheers, > Jérôme > >> Signed-off-by: Christian König <christian.koenig@amd.com> >> --- >> drivers/gpu/drm/radeon/radeon_gem.c | 3 ++- >> drivers/gpu/drm/radeon/radeon_ttm.c | 10 ++++++++++ >> include/uapi/drm/radeon_drm.h | 1 + >> 3 files changed, 13 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c >> index 993ab22..032736b 100644 >> --- a/drivers/gpu/drm/radeon/radeon_gem.c >> +++ b/drivers/gpu/drm/radeon/radeon_gem.c >> @@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data, >> return -EACCES; >> >> /* reject unknown flag values */ >> - if (args->flags & ~RADEON_GEM_USERPTR_READONLY) >> + if (args->flags & ~(RADEON_GEM_USERPTR_READONLY | >> + RADEON_GEM_USERPTR_ANONONLY)) >> return -EINVAL; >> >> /* readonly pages not tested on older hardware */ >> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c >> index 0109090..54eb7bc 100644 >> --- a/drivers/gpu/drm/radeon/radeon_ttm.c >> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c >> @@ -542,6 +542,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) >> ttm->num_pages * PAGE_SIZE)) >> return -EFAULT; >> >> + if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) { >> + /* check that we only pin down anonymous memory >> + to prevent problems with writeback */ >> + unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE; >> + struct vm_area_struct *vma; >> + vma = find_vma(gtt->usermm, gtt->userptr); >> + if (!vma || vma->vm_file || vma->vm_end < end) >> + return -EPERM; >> + } >> + >> do { >> unsigned num_pages = ttm->num_pages - pinned; >> uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE; >> diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h >> index 3a9f209..9720e1a 100644 >> --- a/include/uapi/drm/radeon_drm.h >> +++ b/include/uapi/drm/radeon_drm.h >> @@ -816,6 +816,7 @@ struct drm_radeon_gem_create { >> * perform any operation. >> */ >> #define RADEON_GEM_USERPTR_READONLY (1 << 0) >> +#define RADEON_GEM_USERPTR_ANONONLY (1 << 1) >> >> struct drm_radeon_gem_userptr { >> uint64_t addr; >> -- >> 1.9.1 >> >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/dri-devel
On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > >On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > >>From: Christian König <christian.koenig@amd.com> > >> > >>Avoid problems with writeback by limiting userptr to anonymous memory. > >> > >>v2: add commit and code comments > >I guess, i have not expressed myself clearly. This is bogus, you pretend > >you want to avoid writeback issue but you still allow userspace to map > >file backed pages (which by the way might be a regular bo object from > >another device for instance and that would be fun). > > > >So this patch is a no go and i would rather see that this userptr to > >be restricted to anon vma only no matter what. No flags here. > > Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > with) is restricted to read only access by the GPU. > > I'm fine with making it a hard requirement for all mappings if you say it's > a must have. > Well for time being you should force read only. The way you implement write is broken. Here is how it can abuse to allow write to a file backed mmap. mmap(fixaddress,fixedsize,NOFD) userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) // bo is created successfully because fixedaddress is part of anonvma munmap(fixedaddress,fixedsize) // radeon get mmu_notifier_range_start callback and unbind page from the // bo but radeon does not know there was an unmap. mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) radeon_ioctl_use_my_userptrbo // bo is bind again by radeon and because all flag are set at creation // it is map with write permission allowing someone to write to a file // that might be read only for the user. // // Script kiddies it's time to learn about gpu ... Of course if you this patch (kind of selling my own junk here) : http://www.spinics.net/lists/linux-mm/msg75878.html then you could know inside the range_start that you should remove the write permission and that it should be rechecked on next bind. Note that i have not read much of your code so maybe you handle this case somehow. Cheers, Jérôme > Christian. > > > > >Cheers, > >Jérôme > > > >>Signed-off-by: Christian König <christian.koenig@amd.com> > >>--- > >> drivers/gpu/drm/radeon/radeon_gem.c | 3 ++- > >> drivers/gpu/drm/radeon/radeon_ttm.c | 10 ++++++++++ > >> include/uapi/drm/radeon_drm.h | 1 + > >> 3 files changed, 13 insertions(+), 1 deletion(-) > >> > >>diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c > >>index 993ab22..032736b 100644 > >>--- a/drivers/gpu/drm/radeon/radeon_gem.c > >>+++ b/drivers/gpu/drm/radeon/radeon_gem.c > >>@@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data, > >> return -EACCES; > >> /* reject unknown flag values */ > >>- if (args->flags & ~RADEON_GEM_USERPTR_READONLY) > >>+ if (args->flags & ~(RADEON_GEM_USERPTR_READONLY | > >>+ RADEON_GEM_USERPTR_ANONONLY)) > >> return -EINVAL; > >> /* readonly pages not tested on older hardware */ > >>diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c > >>index 0109090..54eb7bc 100644 > >>--- a/drivers/gpu/drm/radeon/radeon_ttm.c > >>+++ b/drivers/gpu/drm/radeon/radeon_ttm.c > >>@@ -542,6 +542,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) > >> ttm->num_pages * PAGE_SIZE)) > >> return -EFAULT; > >>+ if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) { > >>+ /* check that we only pin down anonymous memory > >>+ to prevent problems with writeback */ > >>+ unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE; > >>+ struct vm_area_struct *vma; > >>+ vma = find_vma(gtt->usermm, gtt->userptr); > >>+ if (!vma || vma->vm_file || vma->vm_end < end) > >>+ return -EPERM; > >>+ } > >>+ > >> do { > >> unsigned num_pages = ttm->num_pages - pinned; > >> uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE; > >>diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h > >>index 3a9f209..9720e1a 100644 > >>--- a/include/uapi/drm/radeon_drm.h > >>+++ b/include/uapi/drm/radeon_drm.h > >>@@ -816,6 +816,7 @@ struct drm_radeon_gem_create { > >> * perform any operation. > >> */ > >> #define RADEON_GEM_USERPTR_READONLY (1 << 0) > >>+#define RADEON_GEM_USERPTR_ANONONLY (1 << 1) > >> struct drm_radeon_gem_userptr { > >> uint64_t addr; > >>-- > >>1.9.1 > >> > >>_______________________________________________ > >>dri-devel mailing list > >>dri-devel@lists.freedesktop.org > >>http://lists.freedesktop.org/mailman/listinfo/dri-devel > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/dri-devel
Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: >> Am 05.08.2014 um 19:39 schrieb Jerome Glisse: >>> On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: >>>> From: Christian König <christian.koenig@amd.com> >>>> >>>> Avoid problems with writeback by limiting userptr to anonymous memory. >>>> >>>> v2: add commit and code comments >>> I guess, i have not expressed myself clearly. This is bogus, you pretend >>> you want to avoid writeback issue but you still allow userspace to map >>> file backed pages (which by the way might be a regular bo object from >>> another device for instance and that would be fun). >>> >>> So this patch is a no go and i would rather see that this userptr to >>> be restricted to anon vma only no matter what. No flags here. >> Mapping of non anonymous memory (e.g. everything get_user_pages won't fail >> with) is restricted to read only access by the GPU. >> >> I'm fine with making it a hard requirement for all mappings if you say it's >> a must have. >> > Well for time being you should force read only. The way you implement write > is broken. Here is how it can abuse to allow write to a file backed mmap. > > mmap(fixaddress,fixedsize,NOFD) > userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > // bo is created successfully because fixedaddress is part of anonvma > munmap(fixedaddress,fixedsize) > // radeon get mmu_notifier_range_start callback and unbind page from the > // bo but radeon does not know there was an unmap. > mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > radeon_ioctl_use_my_userptrbo > // bo is bind again by radeon and because all flag are set at creation > // it is map with write permission allowing someone to write to a file > // that might be read only for the user. > // > // Script kiddies it's time to learn about gpu ... > > Of course if you this patch (kind of selling my own junk here) : > > http://www.spinics.net/lists/linux-mm/msg75878.html > > then you could know inside the range_start that you should remove the > write permission and that it should be rechecked on next bind. > > Note that i have not read much of your code so maybe you handle this > case somehow. I've stumbled over this attack vector as well and it's the reason why I've moved checking the access rights to the bind callback instead of BO creation time with V5 of the patch. This way you get an -EFAULT if you try something like this on command submission time. Regards, Christian. > > Cheers, > Jérôme > >> Christian. >> >>> Cheers, >>> Jérôme >>> >>>> Signed-off-by: Christian König <christian.koenig@amd.com> >>>> --- >>>> drivers/gpu/drm/radeon/radeon_gem.c | 3 ++- >>>> drivers/gpu/drm/radeon/radeon_ttm.c | 10 ++++++++++ >>>> include/uapi/drm/radeon_drm.h | 1 + >>>> 3 files changed, 13 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c >>>> index 993ab22..032736b 100644 >>>> --- a/drivers/gpu/drm/radeon/radeon_gem.c >>>> +++ b/drivers/gpu/drm/radeon/radeon_gem.c >>>> @@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data, >>>> return -EACCES; >>>> /* reject unknown flag values */ >>>> - if (args->flags & ~RADEON_GEM_USERPTR_READONLY) >>>> + if (args->flags & ~(RADEON_GEM_USERPTR_READONLY | >>>> + RADEON_GEM_USERPTR_ANONONLY)) >>>> return -EINVAL; >>>> /* readonly pages not tested on older hardware */ >>>> diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c >>>> index 0109090..54eb7bc 100644 >>>> --- a/drivers/gpu/drm/radeon/radeon_ttm.c >>>> +++ b/drivers/gpu/drm/radeon/radeon_ttm.c >>>> @@ -542,6 +542,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) >>>> ttm->num_pages * PAGE_SIZE)) >>>> return -EFAULT; >>>> + if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) { >>>> + /* check that we only pin down anonymous memory >>>> + to prevent problems with writeback */ >>>> + unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE; >>>> + struct vm_area_struct *vma; >>>> + vma = find_vma(gtt->usermm, gtt->userptr); >>>> + if (!vma || vma->vm_file || vma->vm_end < end) >>>> + return -EPERM; >>>> + } >>>> + >>>> do { >>>> unsigned num_pages = ttm->num_pages - pinned; >>>> uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE; >>>> diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h >>>> index 3a9f209..9720e1a 100644 >>>> --- a/include/uapi/drm/radeon_drm.h >>>> +++ b/include/uapi/drm/radeon_drm.h >>>> @@ -816,6 +816,7 @@ struct drm_radeon_gem_create { >>>> * perform any operation. >>>> */ >>>> #define RADEON_GEM_USERPTR_READONLY (1 << 0) >>>> +#define RADEON_GEM_USERPTR_ANONONLY (1 << 1) >>>> struct drm_radeon_gem_userptr { >>>> uint64_t addr; >>>> -- >>>> 1.9.1 >>>> >>>> _______________________________________________ >>>> dri-devel mailing list >>>> dri-devel@lists.freedesktop.org >>>> http://lists.freedesktop.org/mailman/listinfo/dri-devel >> _______________________________________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.org >> http://lists.freedesktop.org/mailman/listinfo/dri-devel
On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > >On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > >>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > >>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > >>>>From: Christian König <christian.koenig@amd.com> > >>>> > >>>>Avoid problems with writeback by limiting userptr to anonymous memory. > >>>> > >>>>v2: add commit and code comments > >>>I guess, i have not expressed myself clearly. This is bogus, you pretend > >>>you want to avoid writeback issue but you still allow userspace to map > >>>file backed pages (which by the way might be a regular bo object from > >>>another device for instance and that would be fun). > >>> > >>>So this patch is a no go and i would rather see that this userptr to > >>>be restricted to anon vma only no matter what. No flags here. > >>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > >>with) is restricted to read only access by the GPU. > >> > >>I'm fine with making it a hard requirement for all mappings if you say it's > >>a must have. > >> > >Well for time being you should force read only. The way you implement write > >is broken. Here is how it can abuse to allow write to a file backed mmap. > > > >mmap(fixaddress,fixedsize,NOFD) > >userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > >// bo is created successfully because fixedaddress is part of anonvma > >munmap(fixedaddress,fixedsize) > >// radeon get mmu_notifier_range_start callback and unbind page from the > >// bo but radeon does not know there was an unmap. > >mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > >radeon_ioctl_use_my_userptrbo > >// bo is bind again by radeon and because all flag are set at creation > >// it is map with write permission allowing someone to write to a file > >// that might be read only for the user. > >// > >// Script kiddies it's time to learn about gpu ... > > > >Of course if you this patch (kind of selling my own junk here) : > > > >http://www.spinics.net/lists/linux-mm/msg75878.html > > > >then you could know inside the range_start that you should remove the > >write permission and that it should be rechecked on next bind. > > > >Note that i have not read much of your code so maybe you handle this > >case somehow. > > I've stumbled over this attack vector as well and it's the reason why I've > moved checking the access rights to the bind callback instead of BO creation > time with V5 of the patch. > > This way you get an -EFAULT if you try something like this on command > submission time. So you seem immune to that issue but you are still not checking if the anon vma is writeable which you should again security concern here. Cheers, Jérôme
Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: >> Am 06.08.2014 um 00:13 schrieb Jerome Glisse: >>> On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: >>>> Am 05.08.2014 um 19:39 schrieb Jerome Glisse: >>>>> On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: >>>>>> From: Christian König <christian.koenig@amd.com> >>>>>> >>>>>> Avoid problems with writeback by limiting userptr to anonymous memory. >>>>>> >>>>>> v2: add commit and code comments >>>>> I guess, i have not expressed myself clearly. This is bogus, you pretend >>>>> you want to avoid writeback issue but you still allow userspace to map >>>>> file backed pages (which by the way might be a regular bo object from >>>>> another device for instance and that would be fun). >>>>> >>>>> So this patch is a no go and i would rather see that this userptr to >>>>> be restricted to anon vma only no matter what. No flags here. >>>> Mapping of non anonymous memory (e.g. everything get_user_pages won't fail >>>> with) is restricted to read only access by the GPU. >>>> >>>> I'm fine with making it a hard requirement for all mappings if you say it's >>>> a must have. >>>> >>> Well for time being you should force read only. The way you implement write >>> is broken. Here is how it can abuse to allow write to a file backed mmap. >>> >>> mmap(fixaddress,fixedsize,NOFD) >>> userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) >>> // bo is created successfully because fixedaddress is part of anonvma >>> munmap(fixedaddress,fixedsize) >>> // radeon get mmu_notifier_range_start callback and unbind page from the >>> // bo but radeon does not know there was an unmap. >>> mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) >>> radeon_ioctl_use_my_userptrbo >>> // bo is bind again by radeon and because all flag are set at creation >>> // it is map with write permission allowing someone to write to a file >>> // that might be read only for the user. >>> // >>> // Script kiddies it's time to learn about gpu ... >>> >>> Of course if you this patch (kind of selling my own junk here) : >>> >>> http://www.spinics.net/lists/linux-mm/msg75878.html >>> >>> then you could know inside the range_start that you should remove the >>> write permission and that it should be rechecked on next bind. >>> >>> Note that i have not read much of your code so maybe you handle this >>> case somehow. >> I've stumbled over this attack vector as well and it's the reason why I've >> moved checking the access rights to the bind callback instead of BO creation >> time with V5 of the patch. >> >> This way you get an -EFAULT if you try something like this on command >> submission time. > So you seem immune to that issue but you are still not checking if the anon > vma is writeable which you should again security concern here. We check the access rights of the pointer using: > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > (long)gtt->userptr, > ttm->num_pages * PAGE_SIZE)) > return -EFAULT; Shouldn't that be enough? Christian. > > Cheers, > Jérôme
On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: > Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > >On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > >>Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > >>>On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > >>>>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > >>>>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > >>>>>>From: Christian König <christian.koenig@amd.com> > >>>>>> > >>>>>>Avoid problems with writeback by limiting userptr to anonymous memory. > >>>>>> > >>>>>>v2: add commit and code comments > >>>>>I guess, i have not expressed myself clearly. This is bogus, you pretend > >>>>>you want to avoid writeback issue but you still allow userspace to map > >>>>>file backed pages (which by the way might be a regular bo object from > >>>>>another device for instance and that would be fun). > >>>>> > >>>>>So this patch is a no go and i would rather see that this userptr to > >>>>>be restricted to anon vma only no matter what. No flags here. > >>>>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > >>>>with) is restricted to read only access by the GPU. > >>>> > >>>>I'm fine with making it a hard requirement for all mappings if you say it's > >>>>a must have. > >>>> > >>>Well for time being you should force read only. The way you implement write > >>>is broken. Here is how it can abuse to allow write to a file backed mmap. > >>> > >>>mmap(fixaddress,fixedsize,NOFD) > >>>userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > >>>// bo is created successfully because fixedaddress is part of anonvma > >>>munmap(fixedaddress,fixedsize) > >>>// radeon get mmu_notifier_range_start callback and unbind page from the > >>>// bo but radeon does not know there was an unmap. > >>>mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > >>>radeon_ioctl_use_my_userptrbo > >>>// bo is bind again by radeon and because all flag are set at creation > >>>// it is map with write permission allowing someone to write to a file > >>>// that might be read only for the user. > >>>// > >>>// Script kiddies it's time to learn about gpu ... > >>> > >>>Of course if you this patch (kind of selling my own junk here) : > >>> > >>>http://www.spinics.net/lists/linux-mm/msg75878.html > >>> > >>>then you could know inside the range_start that you should remove the > >>>write permission and that it should be rechecked on next bind. > >>> > >>>Note that i have not read much of your code so maybe you handle this > >>>case somehow. > >>I've stumbled over this attack vector as well and it's the reason why I've > >>moved checking the access rights to the bind callback instead of BO creation > >>time with V5 of the patch. > >> > >>This way you get an -EFAULT if you try something like this on command > >>submission time. > >So you seem immune to that issue but you are still not checking if the anon > >vma is writeable which you should again security concern here. > > We check the access rights of the pointer using: > > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > >(long)gtt->userptr, > > ttm->num_pages * PAGE_SIZE)) > > return -EFAULT; > > Shouldn't that be enough? No, access_ok only check against special area on some architecture and i am pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. What you need to test is the vma vm_flags somethings like if (write && !(vma->vm_flags VM_WRITE)) return -EPERM; Which need to happen on all bind. Cheers, Jérôme > > Christian. > > > > >Cheers, > >Jérôme >
On Wed, Aug 06, 2014 at 02:34:16PM -0400, Jerome Glisse wrote: > On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: > > Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > > >On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > > >>Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > > >>>On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > > >>>>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > > >>>>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > > >>>>>>From: Christian König <christian.koenig@amd.com> > > >>>>>> > > >>>>>>Avoid problems with writeback by limiting userptr to anonymous memory. > > >>>>>> > > >>>>>>v2: add commit and code comments > > >>>>>I guess, i have not expressed myself clearly. This is bogus, you pretend > > >>>>>you want to avoid writeback issue but you still allow userspace to map > > >>>>>file backed pages (which by the way might be a regular bo object from > > >>>>>another device for instance and that would be fun). > > >>>>> > > >>>>>So this patch is a no go and i would rather see that this userptr to > > >>>>>be restricted to anon vma only no matter what. No flags here. > > >>>>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > > >>>>with) is restricted to read only access by the GPU. > > >>>> > > >>>>I'm fine with making it a hard requirement for all mappings if you say it's > > >>>>a must have. > > >>>> > > >>>Well for time being you should force read only. The way you implement write > > >>>is broken. Here is how it can abuse to allow write to a file backed mmap. > > >>> > > >>>mmap(fixaddress,fixedsize,NOFD) > > >>>userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > > >>>// bo is created successfully because fixedaddress is part of anonvma > > >>>munmap(fixedaddress,fixedsize) > > >>>// radeon get mmu_notifier_range_start callback and unbind page from the > > >>>// bo but radeon does not know there was an unmap. > > >>>mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > > >>>radeon_ioctl_use_my_userptrbo > > >>>// bo is bind again by radeon and because all flag are set at creation > > >>>// it is map with write permission allowing someone to write to a file > > >>>// that might be read only for the user. > > >>>// > > >>>// Script kiddies it's time to learn about gpu ... > > >>> > > >>>Of course if you this patch (kind of selling my own junk here) : > > >>> > > >>>http://www.spinics.net/lists/linux-mm/msg75878.html > > >>> > > >>>then you could know inside the range_start that you should remove the > > >>>write permission and that it should be rechecked on next bind. > > >>> > > >>>Note that i have not read much of your code so maybe you handle this > > >>>case somehow. > > >>I've stumbled over this attack vector as well and it's the reason why I've > > >>moved checking the access rights to the bind callback instead of BO creation > > >>time with V5 of the patch. > > >> > > >>This way you get an -EFAULT if you try something like this on command > > >>submission time. > > >So you seem immune to that issue but you are still not checking if the anon > > >vma is writeable which you should again security concern here. > > > > We check the access rights of the pointer using: > > > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > > >(long)gtt->userptr, > > > ttm->num_pages * PAGE_SIZE)) > > > return -EFAULT; > > > > Shouldn't that be enough? > > No, access_ok only check against special area on some architecture and i am > pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. > > What you need to test is the vma vm_flags somethings like > > if (write && !(vma->vm_flags VM_WRITE)) > return -EPERM; > > Which need to happen on all bind. > > Cheers, > Jérôme I should add that access_ok should be done only once inside the gem userptr ioctl as access_ok only check that the address is a valid userspace address and not some special address (like an address inside the kernel address space or a non canonical address on x86-64 ...). It it returns true the first time then it will always return true. Only vma need to be checked on each bind. > > > > > Christian. > > > > > > > >Cheers, > > >Jérôme > >
On Wed, Aug 06, 2014 at 02:34:16PM -0400, Jerome Glisse wrote: > On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: > > Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > > >On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > > >>Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > > >>>On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > > >>>>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > > >>>>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > > >>>>>>From: Christian König <christian.koenig@amd.com> > > >>>>>> > > >>>>>>Avoid problems with writeback by limiting userptr to anonymous memory. > > >>>>>> > > >>>>>>v2: add commit and code comments > > >>>>>I guess, i have not expressed myself clearly. This is bogus, you pretend > > >>>>>you want to avoid writeback issue but you still allow userspace to map > > >>>>>file backed pages (which by the way might be a regular bo object from > > >>>>>another device for instance and that would be fun). > > >>>>> > > >>>>>So this patch is a no go and i would rather see that this userptr to > > >>>>>be restricted to anon vma only no matter what. No flags here. > > >>>>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > > >>>>with) is restricted to read only access by the GPU. > > >>>> > > >>>>I'm fine with making it a hard requirement for all mappings if you say it's > > >>>>a must have. > > >>>> > > >>>Well for time being you should force read only. The way you implement write > > >>>is broken. Here is how it can abuse to allow write to a file backed mmap. > > >>> > > >>>mmap(fixaddress,fixedsize,NOFD) > > >>>userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > > >>>// bo is created successfully because fixedaddress is part of anonvma > > >>>munmap(fixedaddress,fixedsize) > > >>>// radeon get mmu_notifier_range_start callback and unbind page from the > > >>>// bo but radeon does not know there was an unmap. > > >>>mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > > >>>radeon_ioctl_use_my_userptrbo > > >>>// bo is bind again by radeon and because all flag are set at creation > > >>>// it is map with write permission allowing someone to write to a file > > >>>// that might be read only for the user. > > >>>// > > >>>// Script kiddies it's time to learn about gpu ... > > >>> > > >>>Of course if you this patch (kind of selling my own junk here) : > > >>> > > >>>http://www.spinics.net/lists/linux-mm/msg75878.html > > >>> > > >>>then you could know inside the range_start that you should remove the > > >>>write permission and that it should be rechecked on next bind. > > >>> > > >>>Note that i have not read much of your code so maybe you handle this > > >>>case somehow. > > >>I've stumbled over this attack vector as well and it's the reason why I've > > >>moved checking the access rights to the bind callback instead of BO creation > > >>time with V5 of the patch. > > >> > > >>This way you get an -EFAULT if you try something like this on command > > >>submission time. > > >So you seem immune to that issue but you are still not checking if the anon > > >vma is writeable which you should again security concern here. > > > > We check the access rights of the pointer using: > > > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > > >(long)gtt->userptr, > > > ttm->num_pages * PAGE_SIZE)) > > > return -EFAULT; > > > > Shouldn't that be enough? > > No, access_ok only check against special area on some architecture and i am > pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. > > What you need to test is the vma vm_flags somethings like > > if (write && !(vma->vm_flags VM_WRITE)) > return -EPERM; > > Which need to happen on all bind. access_ok is _only_ valid in combination with copy_from/to_user and friends and is an optimization of the access checks depending upon architecture. You always need them both, one alone is useless. -Daniel
On Wed, Aug 06, 2014 at 10:24:31PM +0200, Daniel Vetter wrote: > On Wed, Aug 06, 2014 at 02:34:16PM -0400, Jerome Glisse wrote: > > On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: > > > Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > > > >On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > > > >>Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > > > >>>On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > > > >>>>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > > > >>>>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > > > >>>>>>From: Christian König <christian.koenig@amd.com> > > > >>>>>> > > > >>>>>>Avoid problems with writeback by limiting userptr to anonymous memory. > > > >>>>>> > > > >>>>>>v2: add commit and code comments > > > >>>>>I guess, i have not expressed myself clearly. This is bogus, you pretend > > > >>>>>you want to avoid writeback issue but you still allow userspace to map > > > >>>>>file backed pages (which by the way might be a regular bo object from > > > >>>>>another device for instance and that would be fun). > > > >>>>> > > > >>>>>So this patch is a no go and i would rather see that this userptr to > > > >>>>>be restricted to anon vma only no matter what. No flags here. > > > >>>>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > > > >>>>with) is restricted to read only access by the GPU. > > > >>>> > > > >>>>I'm fine with making it a hard requirement for all mappings if you say it's > > > >>>>a must have. > > > >>>> > > > >>>Well for time being you should force read only. The way you implement write > > > >>>is broken. Here is how it can abuse to allow write to a file backed mmap. > > > >>> > > > >>>mmap(fixaddress,fixedsize,NOFD) > > > >>>userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > > > >>>// bo is created successfully because fixedaddress is part of anonvma > > > >>>munmap(fixedaddress,fixedsize) > > > >>>// radeon get mmu_notifier_range_start callback and unbind page from the > > > >>>// bo but radeon does not know there was an unmap. > > > >>>mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > > > >>>radeon_ioctl_use_my_userptrbo > > > >>>// bo is bind again by radeon and because all flag are set at creation > > > >>>// it is map with write permission allowing someone to write to a file > > > >>>// that might be read only for the user. > > > >>>// > > > >>>// Script kiddies it's time to learn about gpu ... > > > >>> > > > >>>Of course if you this patch (kind of selling my own junk here) : > > > >>> > > > >>>http://www.spinics.net/lists/linux-mm/msg75878.html > > > >>> > > > >>>then you could know inside the range_start that you should remove the > > > >>>write permission and that it should be rechecked on next bind. > > > >>> > > > >>>Note that i have not read much of your code so maybe you handle this > > > >>>case somehow. > > > >>I've stumbled over this attack vector as well and it's the reason why I've > > > >>moved checking the access rights to the bind callback instead of BO creation > > > >>time with V5 of the patch. > > > >> > > > >>This way you get an -EFAULT if you try something like this on command > > > >>submission time. > > > >So you seem immune to that issue but you are still not checking if the anon > > > >vma is writeable which you should again security concern here. > > > > > > We check the access rights of the pointer using: > > > > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > > > >(long)gtt->userptr, > > > > ttm->num_pages * PAGE_SIZE)) > > > > return -EFAULT; > > > > > > Shouldn't that be enough? > > > > No, access_ok only check against special area on some architecture and i am > > pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. > > > > What you need to test is the vma vm_flags somethings like > > > > if (write && !(vma->vm_flags VM_WRITE)) > > return -EPERM; > > > > Which need to happen on all bind. > > access_ok is _only_ valid in combination with copy_from/to_user and > friends and is an optimization of the access checks depending upon > architecture. You always need them both, one alone is useless. ENOPARSE, access_ok will always return the same value for a given address at least on x86 so if address supplied at ioctl time is a valid userspace address then it will still be a valid userspace address at buffer object bind time (note that the user address is immutable here). So access_ok can be done once and only once inside the ioctl and then for the write permission you need to recheck the vma each time you bind the object (or rather each time the previous bind was invalidated by some mmu_notifier call). That being said access_ok is kind of useless given that get_user_page will fail on kernel address and i assume for any special address any architecture might have. So strictly speaking the access_ok is just a way to fail early and flatout instead of delaying the failure to bind time. Or do i need to go read x86 code again ? Cheers, Jérôme > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
On Wed, Aug 06, 2014 at 11:45:48PM -0400, Jerome Glisse wrote: > On Wed, Aug 06, 2014 at 10:24:31PM +0200, Daniel Vetter wrote: > > On Wed, Aug 06, 2014 at 02:34:16PM -0400, Jerome Glisse wrote: > > > On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: > > > > Am 06.08.2014 um 18:08 schrieb Jerome Glisse: > > > > >On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: > > > > >>Am 06.08.2014 um 00:13 schrieb Jerome Glisse: > > > > >>>On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: > > > > >>>>Am 05.08.2014 um 19:39 schrieb Jerome Glisse: > > > > >>>>>On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: > > > > >>>>>>From: Christian König <christian.koenig@amd.com> > > > > >>>>>> > > > > >>>>>>Avoid problems with writeback by limiting userptr to anonymous memory. > > > > >>>>>> > > > > >>>>>>v2: add commit and code comments > > > > >>>>>I guess, i have not expressed myself clearly. This is bogus, you pretend > > > > >>>>>you want to avoid writeback issue but you still allow userspace to map > > > > >>>>>file backed pages (which by the way might be a regular bo object from > > > > >>>>>another device for instance and that would be fun). > > > > >>>>> > > > > >>>>>So this patch is a no go and i would rather see that this userptr to > > > > >>>>>be restricted to anon vma only no matter what. No flags here. > > > > >>>>Mapping of non anonymous memory (e.g. everything get_user_pages won't fail > > > > >>>>with) is restricted to read only access by the GPU. > > > > >>>> > > > > >>>>I'm fine with making it a hard requirement for all mappings if you say it's > > > > >>>>a must have. > > > > >>>> > > > > >>>Well for time being you should force read only. The way you implement write > > > > >>>is broken. Here is how it can abuse to allow write to a file backed mmap. > > > > >>> > > > > >>>mmap(fixaddress,fixedsize,NOFD) > > > > >>>userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) > > > > >>>// bo is created successfully because fixedaddress is part of anonvma > > > > >>>munmap(fixedaddress,fixedsize) > > > > >>>// radeon get mmu_notifier_range_start callback and unbind page from the > > > > >>>// bo but radeon does not know there was an unmap. > > > > >>>mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) > > > > >>>radeon_ioctl_use_my_userptrbo > > > > >>>// bo is bind again by radeon and because all flag are set at creation > > > > >>>// it is map with write permission allowing someone to write to a file > > > > >>>// that might be read only for the user. > > > > >>>// > > > > >>>// Script kiddies it's time to learn about gpu ... > > > > >>> > > > > >>>Of course if you this patch (kind of selling my own junk here) : > > > > >>> > > > > >>>http://www.spinics.net/lists/linux-mm/msg75878.html > > > > >>> > > > > >>>then you could know inside the range_start that you should remove the > > > > >>>write permission and that it should be rechecked on next bind. > > > > >>> > > > > >>>Note that i have not read much of your code so maybe you handle this > > > > >>>case somehow. > > > > >>I've stumbled over this attack vector as well and it's the reason why I've > > > > >>moved checking the access rights to the bind callback instead of BO creation > > > > >>time with V5 of the patch. > > > > >> > > > > >>This way you get an -EFAULT if you try something like this on command > > > > >>submission time. > > > > >So you seem immune to that issue but you are still not checking if the anon > > > > >vma is writeable which you should again security concern here. > > > > > > > > We check the access rights of the pointer using: > > > > > if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, > > > > >(long)gtt->userptr, > > > > > ttm->num_pages * PAGE_SIZE)) > > > > > return -EFAULT; > > > > > > > > Shouldn't that be enough? > > > > > > No, access_ok only check against special area on some architecture and i am > > > pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. > > > > > > What you need to test is the vma vm_flags somethings like > > > > > > if (write && !(vma->vm_flags VM_WRITE)) > > > return -EPERM; > > > > > > Which need to happen on all bind. > > > > access_ok is _only_ valid in combination with copy_from/to_user and > > friends and is an optimization of the access checks depending upon > > architecture. You always need them both, one alone is useless. > > ENOPARSE, access_ok will always return the same value for a given address at least > on x86 so if address supplied at ioctl time is a valid userspace address then it > will still be a valid userspace address at buffer object bind time (note that the > user address is immutable here). So access_ok can be done once and only once inside > the ioctl and then for the write permission you need to recheck the vma each time > you bind the object (or rather each time the previous bind was invalidated by some > mmu_notifier call). > > That being said access_ok is kind of useless given that get_user_page will fail on > kernel address and i assume for any special address any architecture might have. So > strictly speaking the access_ok is just a way to fail early and flatout instead of > delaying the failure to bind time. Well that's what I've tried to say. For gup you don't need access_ok, that's really just one part of copy_from/to_user machinery. And afaik it's not specified what exactly access_ok checks (on x86 it only checks for the kernel address limit) so I don't think there's a lot of use in it for gup. Maybe I should have done an s/valid/useful/ in my short comment. -Daniel
Am 07.08.2014 um 08:55 schrieb Daniel Vetter: > On Wed, Aug 06, 2014 at 11:45:48PM -0400, Jerome Glisse wrote: >> On Wed, Aug 06, 2014 at 10:24:31PM +0200, Daniel Vetter wrote: >>> On Wed, Aug 06, 2014 at 02:34:16PM -0400, Jerome Glisse wrote: >>>> On Wed, Aug 06, 2014 at 07:17:25PM +0200, Christian König wrote: >>>>> Am 06.08.2014 um 18:08 schrieb Jerome Glisse: >>>>>> On Wed, Aug 06, 2014 at 08:55:28AM +0200, Christian König wrote: >>>>>>> Am 06.08.2014 um 00:13 schrieb Jerome Glisse: >>>>>>>> On Tue, Aug 05, 2014 at 07:45:21PM +0200, Christian König wrote: >>>>>>>>> Am 05.08.2014 um 19:39 schrieb Jerome Glisse: >>>>>>>>>> On Tue, Aug 05, 2014 at 06:05:29PM +0200, Christian König wrote: >>>>>>>>>>> From: Christian König <christian.koenig@amd.com> >>>>>>>>>>> >>>>>>>>>>> Avoid problems with writeback by limiting userptr to anonymous memory. >>>>>>>>>>> >>>>>>>>>>> v2: add commit and code comments >>>>>>>>>> I guess, i have not expressed myself clearly. This is bogus, you pretend >>>>>>>>>> you want to avoid writeback issue but you still allow userspace to map >>>>>>>>>> file backed pages (which by the way might be a regular bo object from >>>>>>>>>> another device for instance and that would be fun). >>>>>>>>>> >>>>>>>>>> So this patch is a no go and i would rather see that this userptr to >>>>>>>>>> be restricted to anon vma only no matter what. No flags here. >>>>>>>>> Mapping of non anonymous memory (e.g. everything get_user_pages won't fail >>>>>>>>> with) is restricted to read only access by the GPU. >>>>>>>>> >>>>>>>>> I'm fine with making it a hard requirement for all mappings if you say it's >>>>>>>>> a must have. >>>>>>>>> >>>>>>>> Well for time being you should force read only. The way you implement write >>>>>>>> is broken. Here is how it can abuse to allow write to a file backed mmap. >>>>>>>> >>>>>>>> mmap(fixaddress,fixedsize,NOFD) >>>>>>>> userptr_ioctl(fixedaddress, RADEON_GEM_USERPTR_ANONONLY) >>>>>>>> // bo is created successfully because fixedaddress is part of anonvma >>>>>>>> munmap(fixedaddress,fixedsize) >>>>>>>> // radeon get mmu_notifier_range_start callback and unbind page from the >>>>>>>> // bo but radeon does not know there was an unmap. >>>>>>>> mmap(fixaddress,fixedsize,fd_to_this_read_only_file_i_want_to_write_to) >>>>>>>> radeon_ioctl_use_my_userptrbo >>>>>>>> // bo is bind again by radeon and because all flag are set at creation >>>>>>>> // it is map with write permission allowing someone to write to a file >>>>>>>> // that might be read only for the user. >>>>>>>> // >>>>>>>> // Script kiddies it's time to learn about gpu ... >>>>>>>> >>>>>>>> Of course if you this patch (kind of selling my own junk here) : >>>>>>>> >>>>>>>> http://www.spinics.net/lists/linux-mm/msg75878.html >>>>>>>> >>>>>>>> then you could know inside the range_start that you should remove the >>>>>>>> write permission and that it should be rechecked on next bind. >>>>>>>> >>>>>>>> Note that i have not read much of your code so maybe you handle this >>>>>>>> case somehow. >>>>>>> I've stumbled over this attack vector as well and it's the reason why I've >>>>>>> moved checking the access rights to the bind callback instead of BO creation >>>>>>> time with V5 of the patch. >>>>>>> >>>>>>> This way you get an -EFAULT if you try something like this on command >>>>>>> submission time. >>>>>> So you seem immune to that issue but you are still not checking if the anon >>>>>> vma is writeable which you should again security concern here. >>>>> We check the access rights of the pointer using: >>>>>> if (!access_ok(write ? VERIFY_WRITE : VERIFY_READ, >>>>>> (long)gtt->userptr, >>>>>> ttm->num_pages * PAGE_SIZE)) >>>>>> return -EFAULT; >>>>> Shouldn't that be enough? >>>> No, access_ok only check against special area on some architecture and i am >>>> pretty sure on x86 the VERIFY_WRITE or VERIFY_READ is just flat out ignored. >>>> What you need to test is the vma vm_flags somethings like >>>> >>>> if (write && !(vma->vm_flags VM_WRITE)) >>>> return -EPERM; >>>> >>>> Which need to happen on all bind. That seems to be unnecessary, since get_user_pages will check that for us anyway. >>> access_ok is _only_ valid in combination with copy_from/to_user and >>> friends and is an optimization of the access checks depending upon >>> architecture. You always need them both, one alone is useless. >> ENOPARSE, access_ok will always return the same value for a given address at least >> on x86 so if address supplied at ioctl time is a valid userspace address then it >> will still be a valid userspace address at buffer object bind time (note that the >> user address is immutable here). So access_ok can be done once and only once inside >> the ioctl and then for the write permission you need to recheck the vma each time >> you bind the object (or rather each time the previous bind was invalidated by some >> mmu_notifier call). >> >> That being said access_ok is kind of useless given that get_user_page will fail on >> kernel address and i assume for any special address any architecture might have. So >> strictly speaking the access_ok is just a way to fail early and flatout instead of >> delaying the failure to bind time. > Well that's what I've tried to say. For gup you don't need access_ok, > that's really just one part of copy_from/to_user machinery. And afaik it's > not specified what exactly access_ok checks (on x86 it only checks for the > kernel address limit) so I don't think there's a lot of use in it for gup. > > Maybe I should have done an s/valid/useful/ in my short comment. I've dropped the access_ok check and also fixed another bug in the VM handling. Patches are on their way to the list. Thanks for the comments, Christian. > -Daniel
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c index 993ab22..032736b 100644 --- a/drivers/gpu/drm/radeon/radeon_gem.c +++ b/drivers/gpu/drm/radeon/radeon_gem.c @@ -290,7 +290,8 @@ int radeon_gem_userptr_ioctl(struct drm_device *dev, void *data, return -EACCES; /* reject unknown flag values */ - if (args->flags & ~RADEON_GEM_USERPTR_READONLY) + if (args->flags & ~(RADEON_GEM_USERPTR_READONLY | + RADEON_GEM_USERPTR_ANONONLY)) return -EINVAL; /* readonly pages not tested on older hardware */ diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c index 0109090..54eb7bc 100644 --- a/drivers/gpu/drm/radeon/radeon_ttm.c +++ b/drivers/gpu/drm/radeon/radeon_ttm.c @@ -542,6 +542,16 @@ static int radeon_ttm_tt_pin_userptr(struct ttm_tt *ttm) ttm->num_pages * PAGE_SIZE)) return -EFAULT; + if (gtt->userflags & RADEON_GEM_USERPTR_ANONONLY) { + /* check that we only pin down anonymous memory + to prevent problems with writeback */ + unsigned long end = gtt->userptr + ttm->num_pages * PAGE_SIZE; + struct vm_area_struct *vma; + vma = find_vma(gtt->usermm, gtt->userptr); + if (!vma || vma->vm_file || vma->vm_end < end) + return -EPERM; + } + do { unsigned num_pages = ttm->num_pages - pinned; uint64_t userptr = gtt->userptr + pinned * PAGE_SIZE; diff --git a/include/uapi/drm/radeon_drm.h b/include/uapi/drm/radeon_drm.h index 3a9f209..9720e1a 100644 --- a/include/uapi/drm/radeon_drm.h +++ b/include/uapi/drm/radeon_drm.h @@ -816,6 +816,7 @@ struct drm_radeon_gem_create { * perform any operation. */ #define RADEON_GEM_USERPTR_READONLY (1 << 0) +#define RADEON_GEM_USERPTR_ANONONLY (1 << 1) struct drm_radeon_gem_userptr { uint64_t addr;