| Message ID | 20200728014343.341303-1-yepeilin.cs@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [Linux-kernel-mentees] drm/bufs: Prevent kernel-infoleak in copy_one_buf() | expand |
On Tue, Jul 28, 2020 at 3:45 AM Peilin Ye <yepeilin.cs@gmail.com> wrote: > > copy_one_buf() is copying uninitialized stack memory to userspace due to > the compiler not initializing holes in statically allocated structures. > Fix it by initializing `v` with memset(). I would add 'potentially' somewhere in that description: it is architecture dependent whether there are holes in this structure as 'enum' types and 'long' are both dependent on the ABI, and even if there is a hole, it is undefined behavior whether the hold gets initialized. Other than that, the patch looks good. > Cc: stable@vger.kernel.org > Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") > Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> Acked-by: Arnd Bergmann <arnd@arndb.de> > --- > drivers/gpu/drm/drm_bufs.c | 12 ++++++++---- > 1 file changed, 8 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c > index a0735fbc144b..f99cd4a3f951 100644 > --- a/drivers/gpu/drm/drm_bufs.c > +++ b/drivers/gpu/drm/drm_bufs.c > @@ -1349,10 +1349,14 @@ static int copy_one_buf(void *data, int count, struct drm_buf_entry *from) > { > struct drm_buf_info *request = data; > struct drm_buf_desc __user *to = &request->list[count]; > - struct drm_buf_desc v = {.count = from->buf_count, > - .size = from->buf_size, > - .low_mark = from->low_mark, > - .high_mark = from->high_mark}; > + struct drm_buf_desc v; > + > + memset(&v, 0, sizeof(v)); > + > + v.count = from->buf_count; > + v.size = from->buf_size; > + v.low_mark = from->low_mark; > + v.high_mark = from->high_mark; > > if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags))) > return -EFAULT; > -- > 2.25.1 >
On Tue, Jul 28, 2020 at 10:11:09AM +0200, Arnd Bergmann wrote: > On Tue, Jul 28, 2020 at 3:45 AM Peilin Ye <yepeilin.cs@gmail.com> wrote: > > > > copy_one_buf() is copying uninitialized stack memory to userspace due to > > the compiler not initializing holes in statically allocated structures. > > Fix it by initializing `v` with memset(). > > I would add 'potentially' somewhere in that description: it is architecture > dependent whether there are holes in this structure as 'enum' types > and 'long' are both dependent on the ABI, and even if there is a hole, > it is undefined behavior whether the hold gets initialized. I see. I will fix that up. Thank you for the advice! Peilin Ye > Other than that, the patch looks good. > > > Cc: stable@vger.kernel.org > > Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") > > Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> > > Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> > > Acked-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/drivers/gpu/drm/drm_bufs.c b/drivers/gpu/drm/drm_bufs.c index a0735fbc144b..f99cd4a3f951 100644 --- a/drivers/gpu/drm/drm_bufs.c +++ b/drivers/gpu/drm/drm_bufs.c @@ -1349,10 +1349,14 @@ static int copy_one_buf(void *data, int count, struct drm_buf_entry *from) { struct drm_buf_info *request = data; struct drm_buf_desc __user *to = &request->list[count]; - struct drm_buf_desc v = {.count = from->buf_count, - .size = from->buf_size, - .low_mark = from->low_mark, - .high_mark = from->high_mark}; + struct drm_buf_desc v; + + memset(&v, 0, sizeof(v)); + + v.count = from->buf_count; + v.size = from->buf_size; + v.low_mark = from->low_mark; + v.high_mark = from->high_mark; if (copy_to_user(to, &v, offsetof(struct drm_buf_desc, flags))) return -EFAULT;
copy_one_buf() is copying uninitialized stack memory to userspace due to the compiler not initializing holes in statically allocated structures. Fix it by initializing `v` with memset(). Cc: stable@vger.kernel.org Fixes: 5c7640ab6258 ("switch compat_drm_infobufs() to drm_ioctl_kernel()") Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> --- drivers/gpu/drm/drm_bufs.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)