WARNING in udf_map_block

Status: upstream: reported syz repro on 2026/08/16 14:37
Subsystems: udf
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+de2fef01040748da6822@syzkaller.appspotmail.com
First crash: 5d05h, last: 4d23h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
bef50c6c assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ WARNING in udf_map_block 2026/08/13 00:01 2026/08/13 00:01 2026/08/13 01:02 a56bc0a5
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [udf?] WARNING in udf_map_block 0 (1) 2026/08/16 14:37

Sample crash report:
------------[ cut here ]------------
iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB
WARNING: fs/udf/inode.c:355 at udf_map_block+0x38d3/0x4270 fs/udf/inode.c:355, CPU#0: syz.3.600/7227
Modules linked in:
CPU: 0 UID: 0 PID: 7227 Comm: syz.3.600 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:udf_map_block+0x38d3/0x4270 fs/udf/inode.c:355
Code: d3 0e 10 48 3b 84 24 60 03 00 00 75 4e 44 89 f0 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 d4 6c 7c 08 cc e8 fe 1c 65 fe 90 <0f> 0b 90 41 be 8b ff ff ff 48 8b 9c 24 88 00 00 00 eb a5 44 89 e1
RSP: 0018:ffffc90003b5efe0 EFLAGS: 00010293
RAX: ffffffff83628cd2 RBX: 0000000000000003 RCX: ffff888028f80000
RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000003
RBP: ffffc90003b5f390 R08: ffff888028f80000 R09: 0000000000000007
R10: 0000000000000006 R11: ffffffff83629680 R12: ffff8880563f6d28
R13: ffff8880563f6e90 R14: dffffc0000000000 R15: ffffc90003b5f3a8
FS:  00007fa8a824b6c0(0000) GS:ffff888124f0a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f656e3ab000 CR3: 0000000078274000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __udf_get_block+0x52/0x250 fs/udf/inode.c:476
 get_more_blocks fs/direct-io.c:644 [inline]
 do_direct_IO fs/direct-io.c:932 [inline]
 __blockdev_direct_IO+0x1590/0x3380 fs/direct-io.c:1236
 blockdev_direct_IO include/linux/fs.h:3156 [inline]
 udf_direct_IO+0x139/0x200 fs/udf/inode.c:309
 generic_file_read_iter+0x33a/0x560 mm/filemap.c:2993
 copy_splice_read+0x5ff/0xaa0 fs/splice.c:362
 do_splice_read fs/splice.c:979 [inline]
 splice_direct_to_actor+0x4b6/0xcb0 fs/splice.c:1084
 do_splice_direct_actor fs/splice.c:1202 [inline]
 do_splice_direct+0x195/0x290 fs/splice.c:1228
 do_sendfile+0x52e/0x7c0 fs/read_write.c:1371
 __do_sys_sendfile64 fs/read_write.c:1432 [inline]
 __se_sys_sendfile64+0x144/0x1a0 fs/read_write.c:1418
 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: 0033:0x7fa8a739e0d9
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:00007fa8a824b028 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fa8a7626180 RCX: 00007fa8a739e0d9
RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000004
RBP: 00007fa8a7435024 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000e3aa6ea R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa8a7626218 R14: 00007fa8a7626180 R15: 00007fffa55b8de8
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/12 20:32 linux-next 5e6de6a2b522 7ae4acc7 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro] ci-upstream-linux-next-kasan-gce-root WARNING in udf_map_block
2026/08/12 14:35 linux-next 5e6de6a2b522 7ae4acc7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root WARNING in udf_map_block
* Struck through repros no longer work on HEAD.