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Fri, 09 Oct 2026 14:55:30 -0700 (PDT) Date: Fri, 09 Oct 2026 14:55:30 -0700 In-Reply-To: <6a778d6e.9c11d2ce.289b96.00ba.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ac962d2.bbc4c7f9.15faa7.003c.GAE@google.com> Subject: Re: [syzbot] [dri?] WARNING in drm_fbdev_shmem_helper_fb_dirty From: syzbot To: airlied@gmail.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, simona@ffwll.ch, syzkaller-bugs@googlegroups.com, tzimmermann@suse.de Content-Type: text/plain; charset="UTF-8" X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" syzbot has found a reproducer for the following issue on: HEAD commit: af32da41b032 Merge tag 'net-7.3-rc7' of git://git.kernel.o.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17b540a5580000 kernel config: https://syzkaller.appspot.com/x/.config?x=7d1b274ca9837366 dashboard link: https://syzkaller.appspot.com/bug?extid=369ee6a6e9d0bbf14b37 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10c2fa8e580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1268e0a5580000 Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-af32da41.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/6a43965520a9/vmlinux-af32da41.xz kernel image: https://storage.googleapis.com/syzbot-assets/c79ed41c72d4/bzImage-af32da41.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+369ee6a6e9d0bbf14b37@syzkaller.appspotmail.com ------------[ cut here ]------------ virtio-pci 0000:00:01.0: [drm] Dirty helper failed: ret=-12 WARNING: drivers/gpu/drm/drm_fbdev_shmem.c:118 at drm_fbdev_shmem_helper_fb_dirty+0x1e1/0x310 drivers/gpu/drm/drm_fbdev_shmem.c:118, CPU#0: kworker/0:0/9 Modules linked in: CPU: 0 UID: 0 PID: 9 Comm: kworker/0:0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: events drm_fb_helper_damage_work RIP: 0010:drm_fbdev_shmem_helper_fb_dirty+0x288/0x310 drivers/gpu/drm/drm_fbdev_shmem.c:118 Code: 27 fc 4c 89 f8 48 c1 e8 03 42 80 3c 28 00 74 08 4c 89 ff e8 3a 1a 9a fc 4d 8b 27 48 89 df 4c 89 f6 4c 89 e2 8b 5c 24 04 89 d9 <67> 48 0f b9 3a 89 d8 e9 f7 fe ff ff 89 d9 80 e1 07 fe c1 38 c1 0f RSP: 0018:ffffc9000022f898 EFLAGS: 00010246 RAX: 1ffff1100004481a RBX: 00000000fffffff4 RCX: 00000000fffffff4 RDX: ffff888000b33d00 RSI: ffffffff8c79f2a0 RDI: ffffffff91867840 RBP: ffff8880322ca008 R08: ffffc9000022f5e7 R09: 1ffff92000045ebc R10: dffffc0000000000 R11: fffff52000045ebd R12: ffff888000b33d00 R13: dffffc0000000000 R14: ffffffff8c79f2a0 R15: ffff8880002240d0 FS: 0000000000000000(0000) GS:ffff88808b0b4000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f76a6223b50 CR3: 0000000038789000 CR4: 0000000000352ef0 Call Trace: drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:339 [inline] drm_fb_helper_damage_work+0x84c/0xf20 drivers/gpu/drm/drm_fb_helper.c:365 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: fc cld 1: 4c 89 f8 mov %r15,%rax 4: 48 c1 e8 03 shr $0x3,%rax 8: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) d: 74 08 je 0x17 f: 4c 89 ff mov %r15,%rdi 12: e8 3a 1a 9a fc call 0xfc9a1a51 17: 4d 8b 27 mov (%r15),%r12 1a: 48 89 df mov %rbx,%rdi 1d: 4c 89 f6 mov %r14,%rsi 20: 4c 89 e2 mov %r12,%rdx 23: 8b 5c 24 04 mov 0x4(%rsp),%ebx 27: 89 d9 mov %ebx,%ecx * 29: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2e: 89 d8 mov %ebx,%eax 30: e9 f7 fe ff ff jmp 0xffffff2c 35: 89 d9 mov %ebx,%ecx 37: 80 e1 07 and $0x7,%cl 3a: fe c1 inc %cl 3c: 38 c1 cmp %al,%cl 3e: 0f .byte 0xf --- If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing.