Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

drm/nouveau: don't bump pin count on failed re-pin in nouveau_bo_pin_locked()

nouveau_bo_pin_locked() checks whether an already pinned BO is in a memory domain compatible with a new pin request. When the domains are incompatible, it sets -EBUSY but still calls ttm_bo_pin() before returning.

Callers treat a failed nouveau_bo_pin() as not having acquired a new pin, so the extra pin count is never decreased by a matching unpin. This triggers the warning in ttm_bo_release():

WARN_ON_ONCE(bo->pin_count);

Found when fuzzing the nouveau driver with a modified Syzkaller:

WARNING: drivers/gpu/drm/ttm/ttm_bo.c:256 at ttm_bo_release+0x827/0x9e0 drivers/gpu/drm/ttm/ttm_bo.c:256, CPU#1: syz.3.24/2212 Modules linked in: CPU: 1 UID: 0 PID: 2212 Comm: syz.3.24 Not tainted 7.2.0 #24 PREEMPT(lazy) nouveau 0000:01:00.0: gsp:msg fn:103 len:0x40/0x20 res:0x19 resp:0x19 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:ttm_bo_release+0x827/0x9e0 drivers/gpu/drm/ttm/ttm_bo.c:256 Code: 02 00 0f 85 51 01 00 00 48 8b 7b 08 e8 d2 20 01 00 e9 80 fd ff ff e8 d8 15 c0 fe 90 0f 0b 90 e9 e1 f8 ff ff e8 ca 15 c0 fe 90 <0f> 0b 90 e9 a4 f8 ff ff e8 bc 15 c0 fe be 03 00 00 00 4c 89 e7 e8 msg: 00000000: 05 00 d0 c1 04 00 f0 f1 01 30 00 00 2d 90 00 00 .........0..-... RSP: 0018:ffffc9000f5cf710 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff888018e5d2a8 RCX: ffffffff82bb1b36…