Hi, On Thu, Aug 06, 2026 at 07:58:38PM +0200, Vincent Lefevre wrote: > On 2026-08-06 17:37:10 +0000, Debian Bug Tracking System wrote: > > Processing commands for [email protected]: > > > # remote status report for #1116643 (http://bugs.debian.org/1116643) > > > # Bug title: UBSAN: shift-out-of-bounds in > > > .../drivers/gpu/drm/display/drm_dp_mst_topology.c (shift exponent -1) > > > # * https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6303 > > > # * remote status changed: (?) -> closed > > > # * closed upstream > > > tags 1116643 + fixed-upstream > > Bug #1116643 [src:linux] UBSAN: shift-out-of-bounds in > > .../drivers/gpu/drm/display/drm_dp_mst_topology.c (shift exponent -1) > > Added tag(s) fixed-upstream. > > At https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/6303 > there is no indication that the bug was fixed upstream. > > FYI, I got this error only 3 times: > > 2025-09-15T13:17:55+02:00 qaa kernel: UBSAN: shift-out-of-bounds in > /build/reproducible-path/linux-6.16.7/drivers/gpu/drm/display/drm_dp_mst_topology.c:4574:36 > 2025-09-15T13:17:55+02:00 qaa kernel: shift exponent -1 is negative > 2025-09-15T13:17:55+02:00 qaa kernel: CPU: 9 UID: 0 PID: 41777 Comm: > kworker/u64:1 Not tainted 6.16.7+deb14-amd64 #1 PREEMPT(lazy) Debian 6.16.7-1 > > 2025-09-29T10:01:20+02:00 qaa kernel: UBSAN: shift-out-of-bounds in > /build/reproducible-path/linux-6.16.8/drivers/gpu/drm/display/drm_dp_mst_topology.c:4574:36 > 2025-09-29T10:01:20+02:00 qaa kernel: shift exponent -1 is negative > 2025-09-29T10:01:20+02:00 qaa kernel: CPU: 4 UID: 0 PID: 490795 Comm: Xorg > Not tainted 6.16.8+deb14-amd64 #1 PREEMPT(lazy) Debian 6.16.8-1 > > 2025-12-02T09:56:26+01:00 qaa kernel: UBSAN: shift-out-of-bounds in > /build/reproducible-path/linux-6.17.9/drivers/gpu/drm/display/drm_dp_mst_topology.c:4575:36 > 2025-12-02T09:56:26+01:00 qaa kernel: shift exponent -1 is negative > 2025-12-02T09:56:26+01:00 qaa kernel: CPU: 4 UID: 0 PID: 34480 Comm: Xorg Not > tainted 6.17.9+deb14-amd64 #1 PREEMPT(lazy) Debian 6.17.9-1
The fix upstream would be: v7.0-rc1: 342ccffd9f77fc29fe1c05fd145e4d842bd2feaa drm/display/dp_mst: Add protection against 0 vcpi which got backported in turn as well to v6.1.165: 95dbd525efce2a9e9e1c50ad15213de644c85ad0 drm/display/dp_mst: Add protection against 0 vcpi v6.6.128: ac9a7c329a5610051fc476644c9b9145a5965ecb drm/display/dp_mst: Add protection against 0 vcpi v6.12.75: 3f44cdb5371faf225af37d5caba8f21ec0572469 drm/display/dp_mst: Add protection against 0 vcpi v6.18.16: 4d2ccdea18b564e3f73e3e543854acea64e6277d drm/display/dp_mst: Add protection against 0 vcpi (but that is less relevant for this bug, if you are running unstable kernel, so moving to the last kernel in unstable includes the above). Regards, Salvatore
