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