Currently `struct drm_buf_desc` is defined as follows:
struct drm_buf_desc { int count; int size; int low_mark; int high_mark; enum { _DRM_PAGE_ALIGN = 0x01, _DRM_AGP_BUFFER = 0x02, _DRM_SG_BUFFER = 0x04, _DRM_FB_BUFFER = 0x08, _DRM_PCI_BUFFER_RO = 0x10 } flags; unsigned long agp_start; };
copy_one_buf() is potentially copying uninitialized kernel stack memory to userspace, since the compiler may leave such "holes" (around `.flags` and `.agp_start` fields) in this statically allocated structure. Prevent 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 Acked-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Peilin Ye yepeilin.cs@gmail.com --- Change in v2: - Improve commit description. (Suggested 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;