WARNING in fuse_iomap_writeback_range

Status: upstream: reported on 2026/09/26 14:54
Subsystems: fuse
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+e8200299b0556976e13c@syzkaller.appspotmail.com
First crash: 4d09h, last: 4d09h
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ID Workflow Result Correct Bug Created Started Finished Revision
df67602b assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ WARNING in fuse_iomap_writeback_range 2026/09/24 10:32 2026/09/24 10:32 2026/09/24 11:07 3c3cdf19
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Title Replies (including bot) Last reply
[syzbot] [fuse?] WARNING in fuse_iomap_writeback_range 0 (1) 2026/09/26 14:54

Sample crash report:
------------[ cut here ]------------
!ff
WARNING: fs/fuse/file.c:2043 at fuse_write_file_get fs/fuse/file.c:2043 [inline], CPU#0: syz.6.4727/24915
WARNING: fs/fuse/file.c:2043 at fuse_iomap_writeback_range+0x7c8/0x18f0 fs/fuse/file.c:2227, CPU#0: syz.6.4727/24915
Modules linked in:
CPU: 0 UID: 0 PID: 24915 Comm: syz.6.4727 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:fuse_write_file_get fs/fuse/file.c:2043 [inline]
RIP: 0010:fuse_iomap_writeback_range+0x7c8/0x18f0 fs/fuse/file.c:2227
Code: fe 48 83 3b 00 74 5b e8 16 00 6d fe 4c 8b 3c 24 e9 08 0b 00 00 e8 08 00 6d fe eb 5c e8 01 00 6d fe 4c 89 f7 e8 69 c2 8d 08 90 <0f> 0b 90 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 58 80 3c 01 00
RSP: 0018:ffffc9000738f2b8 EFLAGS: 00010286
RAX: 8000000000000000 RBX: ffff888057eb0d80 RCX: ffffffff9a9e9501
RDX: 0000000000000001 RSI: 0000000000000004 RDI: 00000000ffffffff
RBP: 0000000000001000 R08: ffff888057eb1363 R09: 1ffff1100afd626c
R10: dffffc0000000000 R11: ffffed100afd626d R12: ffff888057eb1208
R13: 0000000000001000 R14: ffff888057eb1360 R15: ffff888057eb1208
FS:  00007fc6e84ad6c0(0000) GS:ffff888124ccb000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f22f05eb840 CR3: 000000007d23c000 CR4: 00000000003526f0
DR0: 0000000000000008 DR1: 0000000000000002 DR2: 0000000000000404
DR3: ffffffffefffff14 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 iomap_writeback_range fs/iomap/buffered-io.c:1896 [inline]
 iomap_writeback_folio+0x1526/0x2490 fs/iomap/buffered-io.c:2022
 fuse_launder_folio+0x17b/0x240 fs/fuse/file.c:2331
 folio_launder mm/truncate.c:612 [inline]
 folio_unmap_invalidate+0x4cd/0x830 mm/truncate.c:634
 invalidate_inode_pages2_range+0x629/0xb30 mm/truncate.c:726
 fuse_open+0x5a6/0x770 fs/fuse/file.c:297
 do_dentry_open+0x816/0x1380 fs/open.c:996
 vfs_open+0x3b/0x340 fs/open.c:1101
 do_open fs/namei.c:4837 [inline]
 path_openat+0x1443/0x1d60 fs/namei.c:5000
 do_file_open+0x23e/0x4a0 fs/namei.c:5029
 do_sys_openat2+0x115/0x200 fs/open.c:1417
 do_sys_open fs/open.c:1423 [inline]
 __do_sys_openat fs/open.c:1439 [inline]
 __se_sys_openat fs/open.c:1434 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1434
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6e759e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc6e84ad028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc6e7826090 RCX: 00007fc6e759e159
RDX: 0000000000000040 RSI: 000020000000c380 RDI: ffffffffffffff9c
RBP: 00007fc6e763506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc6e7826128 R14: 00007fc6e7826090 R15: 00007fc6e794fa48
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/22 14:44 upstream f0100363d8c3 e12281bd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce WARNING in fuse_iomap_writeback_range
* Struck through repros no longer work on HEAD.