From nobody Fri Sep 25 19:22:10 2026 Received: from smtpbgbr1.qq.com (smtpbgbr1.qq.com [54.207.19.206]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C50B037F006; Wed, 9 Sep 2026 09:11:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=54.207.19.206 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788945117; cv=none; b=O6y011+KsMIyh8OO+QrcJ9hgbwUNt/VVEjheDQXqptkCIK+p4z0CXLyzBpWQacURAfcvmXI+FWwl2QTmj1weLE3cM053NCw4OBh70JZfQne6WNzamjHgfSSbnIPkmckp6Np/pX3n5gx6loyrbMAjX80sryaS40QVQHJ/qrpyd9A= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788945117; c=relaxed/simple; bh=1wLbBjx0R0JxlU+UMv1TAs5nGm6HEqYp53dkIfZRlzU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=LJQ4g6nZggi7qQNtEQX9BJno/1tIYxicfaaMpb9Npqnd8C9SKHbltoiwFnDxmCNBuUbufCLnC+Qgqg+At0kUmRPpl0c0TbqszQbkrpBqxW8WD3/tcyQB+cjJRpGEL9SfXX7y5UQ6aTC81Wk3K81EJEXiR0KZGw80DPmvQ4YLYYo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=smail.nju.edu.cn; spf=pass smtp.mailfrom=smail.nju.edu.cn; dkim=pass (1024-bit key) header.d=smail.nju.edu.cn header.i=@smail.nju.edu.cn header.b=4Ak/dYKX; arc=none smtp.client-ip=54.207.19.206 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=smail.nju.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=smail.nju.edu.cn Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=smail.nju.edu.cn header.i=@smail.nju.edu.cn header.b="4Ak/dYKX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=smail.nju.edu.cn; s=iohv2404; t=1788945096; bh=yw5NGiijZ5YALpYySw4SpwKyTfmc247roOEcNi54jXw=; h=From:To:Subject:Date:Message-ID:MIME-Version; b=4Ak/dYKXNCnci2o1xofVaLbF+zLGCUpnlNk96HuMYPy1mjjs+cpn8LHU9Mpe5zjDj 3WnsL77CSsWds2mR3qDAmdOnXtAyEh3AKpCbIRoy2llw9XfhKAozEWFfxrHJeb9ygU PsbKjIjt3rahdA8eR/51CC5FPzvGv2zvaVlhWswE= X-QQ-mid: zesmtpsz6t1788945079t3aeb69b1 X-QQ-Originating-IP: DI5LWWLOhAhhqOxp8nE4wrAGDVtZXMdzF1lEklLG0UY= Received: from hepeiyang-vm.wu.lxd ( [114.212.83.113]) by bizesmtp.qq.com (ESMTP) with id ; Wed, 09 Sep 2026 17:11:16 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 1 X-BIZMAIL-ID: 12982179329491539308 EX-QQ-RecipientCnt: 13 From: Peiyang He To: airlied@redhat.com, kraxel@redhat.com, dmitry.osipenko@collabora.com, dri-devel@lists.freedesktop.org Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, virtualization@lists.linux.dev, gurchetansingh@chromium.org, olvaffe@gmail.com, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, Peiyang He Subject: [PATCH] drm/virtio: fix NULL pointer dereference on fence allocation failure Date: Wed, 9 Sep 2026 17:11:14 +0800 Message-ID: <00EFE4BA92889B14+20260909091114.2622550-1-peiyang_he@smail.nju.edu.cn> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-QQ-SENDSIZE: 520 Feedback-ID: zesmtpsz:smail.nju.edu.cn:qybglogicsvrsz:qybglogicsvrsz4b-0 X-QQ-XMAILINFO: ORP1oqzHuvxW1imbPWOGoPtqzqrJQv/7nhd0d5XpM0LEt1fd/4NElgZ2 YUfsAGeZqnqjgUHkT846YUyr6W4vmNZ+iMpRi+eeO8IT+U+UqIaz5z8YLisTZUFjoxJBH2U fEM9I1erxAbirE0Zi7/q8jfJ9JZjRHIUpWGggMUazb/LVjSUWTSTdUn6wH9WAJ5l2EW/8AZ 3VNZV9l1o8OUaJ1K9ghbt4Bp4UqYzEXeMUDsNnD/onabev4aDW6bWVT4aZN8QDob0SAnSEh UWVYq1HCdqooDTYzu4DsrCdeXhHYQURwV8cp0iK/01XOqP7DmFZ/LJpexUf15fj7qEct0B6 Q0bXz1SyPHNT/WXh7uwl3hnaBVuMrMxgKSbm3zgH9SbKAHOnxUSzPAgaa4MHS9OICYkMGD6 RDEuq8ju/SYNUVZKuhQv03sFpFYFRvza99OM+a0zawRjYEbTjboV0qCN5ETkhFTON8AmAqG /9RxcHV/iN3/pC+GoIivYfZMttXyb17HKs4ag7CTUpzvDzD0iQ/FiJk1ijUQskpUWpEr0ZC iCMDF7PzVbfDqK3IiKEUTTVw7gsCm3vRMxBqLfX+FN1U4ek1IlUeM8Gw2lh21Nk+X7jjlBW gYN/qJ+BEmfSb9XlaVey5aS9Sanz4Zixj/MRqLD4Gp+7K+wyzEGJT5rjRN/KSADqznty80T lT48Wsnf/ZQ/KJsgaKHom/N2X7gKqFhlAj9W16cexGRrp2foRZfHyvGRvSHVETsY6dUItZq QKACvYgr1N1AZ7MbMXqZJ/RFLWrP+bLE5SGHAQeGS1XEJiBkTFuzFyu1PXcRWRjq7PQgIOs 6MkcEuHRMPP7meMjVu4iqDPoUM4Z0cHwl2Kc5tfhCI+JEW7UwIABFPcRYP3qE/g/OJcGdD6 sgaR+MmvsC3nasPjTT5mTe6NvxcTU0GgBHH9D+KkhwaxogWjcyPIfB3d1L8v52lB2RzZZHi +RRjfuPQEOpPVs5ytELmhdZngftt6KtoyqpWlPl1o+EjkQ6vpPrqXcvhXi2Xx00NL2lslqQ e37GgUA/NjlU2d2eB/aA+RK7Saf2f+F6aqBB1Yh7K/LRi4CGkEjDQ+i70vCis= X-QQ-XMRINFO: OWPUhxQsoeAVwkVaQIEGSKwwgKCxK/fD5g== X-QQ-RECHKSPAM: 0 Content-Type: text/plain; charset="utf-8" virtio_gpu_fence_alloc() can fail due to memory pressure and return NULL, but its caller like virtio_gpu_init_submit() never checks it. Later, virtio_gpu_init_submit() passes the NULL fence to virtio_gpu_fence_event_create(), which unconditionally dereferences it. Found when fuzzing the virtio driver with Syzkaller: Oops: general protection fault, probably for non-canonical address 0xdffff= c0000000012: 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)=20 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52= ca86e094d-prebuilt.qemu.org 04/01/2014 RIP: 0010:virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_sub= mit.c:295 [inline] RIP: 0010:virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:3= 98 [inline] RIP: 0010:virtio_gpu_execbuffer_ioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/= virtgpu_submit.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 R0virtio_gpu_virgl_process_cmd: ctrl 0x102, error 0x= 1203 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880132c4000 R13: 0000000000000000 R14: ffff888073b6c700 R15: 000000000000003b FS: 00007fab480b96c0(0000) GS:ffff8880eb6e9000(0000) knlGS:00000000000000= 00 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007effbf5e55a8 CR3: 0000000048d19000 CR4: 0000000000350ef0 Call Trace: drm_ioctl_kernel+0x1f4/0x3e0 drivers/gpu/drm/drm_ioctl.c:817 drm_ioctl+0x5f4/0xc70 drivers/gpu/drm/drm_ioctl.c:914 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x116/0x800 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+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 ORIG_RAX: 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 Modules linked in: ---[ end trace 0000000000000000 ]--- RIP: 0010:virtio_gpu_fence_event_create drivers/gpu/drm/virtio/virtgpu_sub= mit.c:295 [inline] RIP: 0010:virtio_gpu_init_submit drivers/gpu/drm/virtio/virtgpu_submit.c:3= 98 [inline] RIP: 0010:virtio_gpu_execbuffer_ioctl+0xc78/0x1aa0 drivers/gpu/drm/virtio/= virtgpu_submit.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:00000000000000= 00 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f24c3759000 CR3: 0000000048d19000 CR4: 0000000000350ef0 ---------------- Code disassembly (best guess): 0: 85 ed test %ebp,%ebp 2: 0f 85 21 09 00 00 jne 0x929 8: e8 05 5a c9 fb call 0xfbc95a12 d: 48 8b 44 24 10 mov 0x10(%rsp),%rax 12: 48 8d b8 90 00 00 00 lea 0x90(%rax),%rdi 19: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 20: fc ff df 23: 48 89 fa mov %rdi,%rdx 26: 48 c1 ea 03 shr $0x3,%rdx * 2a: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruc= tion 2e: 0f 85 9a 0d 00 00 jne 0xdce 34: 48 8b 44 24 10 mov 0x10(%rsp),%rax 39: 4c 89 b0 90 00 00 00 mov %r14,0x90(%rax) Fix by checking virtio_gpu_fence_alloc() in virtio_gpu_init_submit() and returning -ENOMEM before any later code can dereference the NULL fence. Fixes: 70d1ace56db6 ("drm/virtio: Conditionally allocate virtio_gpu_fence") Cc: stable@vger.kernel.org Signed-off-by: Peiyang He Assisted-by: Codex:gpt-5.5 --- drivers/gpu/drm/virtio/virtgpu_submit.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_submit.c b/drivers/gpu/drm/virt= io/virtgpu_submit.c index 32cb1e4aa425..857ed5c5f2a8 100644 --- a/drivers/gpu/drm/virtio/virtgpu_submit.c +++ b/drivers/gpu/drm/virtio/virtgpu_submit.c @@ -389,10 +389,13 @@ static int virtio_gpu_init_submit(struct virtio_gpu_s= ubmit *submit, if ((exbuf->flags & VIRTGPU_EXECBUF_FENCE_FD_OUT) || exbuf->num_out_syncobjs || exbuf->num_bo_handles || - drm_fence_event) + drm_fence_event) { out_fence =3D virtio_gpu_fence_alloc(vgdev, fence_ctx, ring_idx); - else + if (!out_fence) + return -ENOMEM; + } else { out_fence =3D NULL; + } =20 if (drm_fence_event) { err =3D virtio_gpu_fence_event_create(dev, file, out_fence, ring_idx); --=20 2.43.0