CVE-2026-98508: drm/virtio: fix NULL pointer dereference on fence allocation failure
In the Linux kernel, the following vulnerability has been resolved:
drm/virtio: fix NULL pointer dereference on fence allocation failure
virtiogpufencealloc() can fail due to memory pressure and return NULL, but its caller like virtiogpuinitsubmit() never checks it. Later, virtiogpuinitsubmit() passes the NULL fence to virtiogpufenceeventcreate(), which unconditionally dereferences it.
Found when fuzzing the virtio driver with Syzkaller:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000012: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000090-0x0000000000000097] CPU: 1 UID: 0 PID: 9991 Comm: syz.0.121 Not tainted 7.2.0 #4 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014 RIP: 0010:virtiogpufenceeventcreate drivers/gpu/drm/virtio/virtgpusubmit.c:295 [inline] RIP: 0010:virtiogpuinitsubmit drivers/gpu/drm/virtio/virtgpusubmit.c:398 [inline] RIP: 0010:virtiogpuexecbufferioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/virtgpusubmit.c:505 Code: 85 ed 0f 85 21 09 00 00 e8 05 5a c9 fb 48 8b 44 24 10 48 8d b8 90 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 9a 0d 00 00 48 8b 44 24 10 4c 89 b0 90 00 00 00 RSP: 0018:ffffc900039dfad0 EFLAGS: 00010216 RAX: dffffc0000000000 RBX: ffffc900039dfdd8 RCX: ffffffff85f6fd3d RDX: 0000000000000012 RSI: ffffffff85f6fd4b RDI: 0000000000000090 RBP: 0000000000000000 R0virtiogpuvirglprocesscmd: ctrl 0x102, error 0x1203 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880132c4000 R13: 0000000000000000 R14: ffff888073b6c700 R15: 000000000000003b FS: 00007fab480b96c0(0000) GS:ffff8880eb6e9000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007effbf5e55a8 CR3: 0000000048d19000 CR4: 0000000000350ef0 Call Trace: <TASK> drmioctlkernel+0x1f4/0x3e0 drivers/gpu/drm/drmioctl.c:817 drmioctl+0x5f4/0xc70 drivers/gpu/drm/drmioctl.c:914 vfsioctl fs/ioctl.c:51 [inline] dosysioctl fs/ioctl.c:597 [inline] sesysioctl fs/ioctl.c:583 [inline] x64sysioctl+0x18e/0x210 fs/ioctl.c:583 dosyscallx64 arch/x86/entry/syscall64.c:63 [inline] dosyscall64+0x116/0x800 arch/x86/entry/syscall64.c:94 entrySYSCALL64afterhwframe+0x77/0x7f RIP: 0033:0x7fab471a82bd Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fab480b9018 EFLAGS: 00000246 ORIGRAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007fab47435fa0 RCX: 00007fab471a82bd RDX: 00002000000000c0 RSI: 00000000c0406442 RDI: 0000000000000003 RBP: 00007fab480b9080 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007fab47436038 R14: 00007fab47435fa0 R15: 00007ffe85ab0740 </TASK> Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:virtiogpufenceeventcreate drivers/gpu/drm/virtio/virtgpusubmit.c:295 [inline] RIP: 0010:virtiogpuinitsubmit drivers/gpu/drm/virtio/virtgpusubmit.c:398 [inline] RIP: 0010:virtiogpuexecbufferioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/virtgpusubmit.c:505 Code: 85 ed 0f 85 21 09 00 00 e8 05 5a c9 fb 48 8b 44 24 10 48 8d b8 90 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 9a 0d 00 00 48 8b 44 24 10 4c 89 b0 90 00 00 00 RSP: 0018:ffffc900039dfad0 EFLAGS: 00010216 RAX: dffffc0000000000 RBX: ffffc900039dfdd8 RCX: ffffffff85f6fd3d RDX: 0000000000000012 RSI: ffffffff85f6fd4b RDI: 0000000000000090 RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880132c4000 R13: 0000000000000000 R14: ffff888073b6c700 R15: 000000000000003b FS: 00007fab480b96c0(0000) GS:ffff888098ae9000(0000) knlGS:00000000 ---truncated---