| Message ID | 20220824142634.20966-1-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | xen/privcmd: fix error exit of privcmd_ioctl_dm_op() | expand |
On 24.08.22 17:26, Juergen Gross wrote: Hello Juergen > The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() > potentially with pages being NULL, leading to a NULL dereference. > > Fix that by calling unlock_pages only if lock_pages() was at least > partially successful. > > Cc: <stable@vger.kernel.org> > Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP") > Reported-by: Rustam Subkhankulov <subkhankulov@ispras.ru> > Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com> > --- > drivers/xen/privcmd.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c > index 3369734108af..ec87968b4459 100644 > --- a/drivers/xen/privcmd.c > +++ b/drivers/xen/privcmd.c > @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) > rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned); > if (rc < 0) { > nr_pages = pinned; > - goto out; > + goto unlock; > } > > for (i = 0; i < kdata.num; i++) { > @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) > rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs); > xen_preemptible_hcall_end(); > > -out: > + unlock: > unlock_pages(pages, nr_pages); > + out: > kfree(xbufs); > kfree(pages); > kfree(kbufs);
On 24.08.2022 16:26, Juergen Gross wrote: > The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() > potentially with pages being NULL, leading to a NULL dereference. > > Fix that by calling unlock_pages only if lock_pages() was at least > partially successful. > > Cc: <stable@vger.kernel.org> > Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP") > Reported-by: Rustam Subkhankulov <subkhankulov@ispras.ru> > Signed-off-by: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> albeit I wonder whether you did consider the variant actually reducing code size (and avoiding the need for yet another label), ... > --- a/drivers/xen/privcmd.c > +++ b/drivers/xen/privcmd.c > @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) > rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned); > if (rc < 0) { > nr_pages = pinned; ... dropping this line and ... > - goto out; > + goto unlock; > } > > for (i = 0; i < kdata.num; i++) { > @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) > rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs); > xen_preemptible_hcall_end(); > > -out: > + unlock: > unlock_pages(pages, nr_pages); ... passing "pinned" here. Jan > + out: > kfree(xbufs); > kfree(pages); > kfree(kbufs);
On 25.08.22 09:38, Jan Beulich wrote: > On 24.08.2022 16:26, Juergen Gross wrote: >> The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() >> potentially with pages being NULL, leading to a NULL dereference. >> >> Fix that by calling unlock_pages only if lock_pages() was at least >> partially successful. >> >> Cc: <stable@vger.kernel.org> >> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP") >> Reported-by: Rustam Subkhankulov <subkhankulov@ispras.ru> >> Signed-off-by: Juergen Gross <jgross@suse.com> > > Reviewed-by: Jan Beulich <jbeulich@suse.com> > albeit I wonder whether you did consider the variant actually > reducing code size (and avoiding the need for yet another label), > ... > >> --- a/drivers/xen/privcmd.c >> +++ b/drivers/xen/privcmd.c >> @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) >> rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned); >> if (rc < 0) { >> nr_pages = pinned; > > ... dropping this line and ... > >> - goto out; >> + goto unlock; >> } >> >> for (i = 0; i < kdata.num; i++) { >> @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) >> rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs); >> xen_preemptible_hcall_end(); >> >> -out: >> + unlock: >> unlock_pages(pages, nr_pages); > > ... passing "pinned" here. Looking into this I found another problem: NOT using pinned is wrong, as lock_pages() doesn't guarantee that all pages were really locked. I think lock_pages() should return an error, in case pin_user_pages_fast() didn't lock as many pages es expected. Juergen
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c index 3369734108af..ec87968b4459 100644 --- a/drivers/xen/privcmd.c +++ b/drivers/xen/privcmd.c @@ -679,7 +679,7 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) rc = lock_pages(kbufs, kdata.num, pages, nr_pages, &pinned); if (rc < 0) { nr_pages = pinned; - goto out; + goto unlock; } for (i = 0; i < kdata.num; i++) { @@ -691,8 +691,9 @@ static long privcmd_ioctl_dm_op(struct file *file, void __user *udata) rc = HYPERVISOR_dm_op(kdata.dom, kdata.num, xbufs); xen_preemptible_hcall_end(); -out: + unlock: unlock_pages(pages, nr_pages); + out: kfree(xbufs); kfree(pages); kfree(kbufs);
The error exit of privcmd_ioctl_dm_op() is calling unlock_pages() potentially with pages being NULL, leading to a NULL dereference. Fix that by calling unlock_pages only if lock_pages() was at least partially successful. Cc: <stable@vger.kernel.org> Fixes: ab520be8cd5d ("xen/privcmd: Add IOCTL_PRIVCMD_DM_OP") Reported-by: Rustam Subkhankulov <subkhankulov@ispras.ru> Signed-off-by: Juergen Gross <jgross@suse.com> --- drivers/xen/privcmd.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)