4.18-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
commit 12d43deb1ee639d01a2a8d2a7a4cc8ad31224475 upstream.
fd_install() moves the reference given to it into the file descriptor table of the current process. If the current process is multithreaded, then immediately after fd_install(), another thread can close() the file descriptor and cause the file's resources to be cleaned up.
Since the reference to "lessee" is held by the file, we must not access "lessee" after the fd_install() call.
As far as I can tell, to reach this codepath, the caller must have an open file descriptor to a DRI device in master mode. I'm not sure what the requirements for that are.
Signed-off-by: Jann Horn jannh@google.com Fixes: 62884cd386b8 ("drm: Add four ioctls for managing drm mode object leases [v7]") Cc: stable@vger.kernel.org Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch Link: https://patchwork.freedesktop.org/patch/msgid/20181001153117.216923-1-jannh@... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/gpu/drm/drm_lease.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/drm_lease.c +++ b/drivers/gpu/drm/drm_lease.c @@ -566,14 +566,14 @@ int drm_mode_create_lease_ioctl(struct d lessee_priv->is_master = 1; lessee_priv->authenticated = 1;
- /* Hook up the fd */ - fd_install(fd, lessee_file); - /* Pass fd back to userspace */ DRM_DEBUG_LEASE("Returning fd %d id %d\n", fd, lessee->lessee_id); cl->fd = fd; cl->lessee_id = lessee->lessee_id;
+ /* Hook up the fd */ + fd_install(fd, lessee_file); + DRM_DEBUG_LEASE("drm_mode_create_lease_ioctl succeeded\n"); return 0;