Messages in this thread | | | Date | Fri, 31 Jul 2020 08:53:22 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [Linux-kernel-mentees] [PATCH] drm/amdgpu: Prevent kernel-infoleak in amdgpu_info_ioctl() |
| |
On Thu, Jul 30, 2020 at 05:09:07PM -0400, Luben Tuikov wrote: > On 2020-07-29 9:49 a.m., Alex Deucher wrote: > > On Wed, Jul 29, 2020 at 4:11 AM Christian König > > <ckoenig.leichtzumerken@gmail.com> wrote: > >> > >> Am 28.07.20 um 21:29 schrieb Peilin Ye: > >>> Compiler leaves a 4-byte hole near the end of `dev_info`, causing > >>> amdgpu_info_ioctl() to copy uninitialized kernel stack memory to userspace > >>> when `size` is greater than 356. > >>> > >>> In 2015 we tried to fix this issue by doing `= {};` on `dev_info`, which > >>> unfortunately does not initialize that 4-byte hole. Fix it by using > >>> memset() instead. > >>> > >>> Cc: stable@vger.kernel.org > >>> Fixes: c193fa91b918 ("drm/amdgpu: information leak in amdgpu_info_ioctl()") > >>> Fixes: d38ceaf99ed0 ("drm/amdgpu: add core driver (v4)") > >>> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> > >>> Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com> > >> > >> Reviewed-by: Christian König <christian.koenig@amd.com> > >> > >> I can't count how many of those we have fixed over the years. > >> > >> At some point we should probably document that using "= {}" or "= { 0 }" > >> in the kernel is a really bad idea and should be avoided. > > > > Moreover, it seems like different compilers seem to behave relatively > > differently with these and we often get reports of warnings with these > > on clang. When in doubt, memset. > > There are quite a few of those under drivers/gpu/drm, for "amd/", "scheduler/" > drm*.c files, > > $find . \( -regex "./drm.*\.c" -or -regex "./amd/.*\.c" -or -regex "./scheduler/.*\.c" \) -exec egrep -n -- " *= *{ *(|NULL|0) *}" \{\} \+ | wc -l > 374 > $_ > > Out of which only 16 are of the non-ISO C variety, "= {}", > > $find . \( -regex "./drm.*\.c" -or -regex "./amd/.*\.c" -or -regex "./scheduler/.*\.c" \) -exec egrep -n -- " *= *{ *}" \{\} \+ | wc -l > 16 > $_ > > Perhaps the latter are the more pressing ones, since it is a C++ initializer and not a ISO C one.
It only matters when we care copying the data to userspace, if it all stays in the kernel, all is fine.
thanks,
greg k-h
| |