KASAN: null-ptr-deref Read in txBeginAnon

Status: upstream: reported C repro on 2025/10/21 23:24
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ac8e393d0a3cf40631cd@syzkaller.appspotmail.com
First crash: 276d, last: 104d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/10/22 linux-6.6.y (ToT) f231f248323d C [report] KASAN: null-ptr-deref Read in txBeginAnon
2025/10/22 upstream (ToT) 552c50713f27 C Didn't crash
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: unable to handle kernel paging request in txBeginAnon jfs 11 C inconclusive 43 502d 791d 28/29 fixed on 2025/06/10 16:19
linux-5.15 BUG: unable to handle kernel paging request in txBeginAnon missing-backport origin:upstream 11 C error 42 12d 566d 0/3 upstream: reported C repro on 2025/01/04 14:54
linux-6.1 BUG: unable to handle kernel paging request in txBeginAnon origin:upstream missing-backport 11 C inconclusive 48 41d 587d 0/3 upstream: reported C repro on 2024/12/14 17:41
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/10/27 12:23 3h26m fix candidate upstream OK (0) job log

Sample crash report:
jfs_dirty_inode called on read-only volume
Is remount racy?
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: null-ptr-deref in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
BUG: KASAN: null-ptr-deref in txBeginAnon+0x16d/0x3b0 fs/jfs/jfs_txnmgr.c:465
Read of size 8 at addr 0000000000000040 by task syz.0.17/5949

CPU: 1 PID: 5949 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x288/0x290 mm/kasan/generic.c:187
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 txBeginAnon+0x16d/0x3b0 fs/jfs/jfs_txnmgr.c:465
 extAlloc+0xf7/0xf30 fs/jfs/jfs_extent.c:78
 jfs_get_block+0x347/0xab0 fs/jfs/inode.c:248
 get_more_blocks fs/direct-io.c:647 [inline]
 do_direct_IO fs/direct-io.c:935 [inline]
 __blockdev_direct_IO+0x1679/0x3420 fs/direct-io.c:1248
 blockdev_direct_IO include/linux/fs.h:3047 [inline]
 jfs_direct_IO+0x11b/0x220 fs/jfs/inode.c:331
 generic_file_direct_write+0x1d4/0x3e0 mm/filemap.c:3941
 __generic_file_write_iter+0x11b/0x230 mm/filemap.c:4097
 generic_file_write_iter+0xaf/0x2e0 mm/filemap.c:4137
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x79a/0xc70 fs/read_write.c:860
 iter_file_splice_write+0x66f/0xc50 fs/splice.c:736
 do_splice_from fs/splice.c:933 [inline]
 direct_splice_actor+0xe8/0x130 fs/splice.c:1142
 splice_direct_to_actor+0x2f0/0x870 fs/splice.c:1088
 do_splice_direct+0x1b7/0x2c0 fs/splice.c:1194
 do_sendfile+0x5dc/0xf70 fs/read_write.c:1254
 __do_sys_sendfile64 fs/read_write.c:1322 [inline]
 __se_sys_sendfile64+0x13f/0x190 fs/read_write.c:1308
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcb7958efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd0e5cc858 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fcb797e5fa0 RCX: 00007fcb7958efc9
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000005
RBP: 00007fcb79611f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000020fffe82 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcb797e5fa0 R14: 00007fcb797e5fa0 R15: 0000000000000004
 </TASK>
==================================================================

Crashes (10):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/22 00:20 linux-6.6.y f231f248323d 9832ed61 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2025/10/21 23:52 linux-6.6.y f231f248323d 9832ed61 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2026/04/11 12:27 linux-6.6.y 80de0a958133 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2026/04/11 12:25 linux-6.6.y 80de0a958133 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2026/04/06 07:38 linux-6.6.y c09fbcd31ae6 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2026/04/06 07:37 linux-6.6.y c09fbcd31ae6 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2026/02/05 20:34 linux-6.6.y 2cf6f68313dc 4936e85c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2025/10/24 01:27 linux-6.6.y 4a243110dc88 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2025/10/21 23:23 linux-6.6.y f231f248323d 9832ed61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
2025/10/21 23:23 linux-6.6.y f231f248323d 9832ed61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: null-ptr-deref Read in txBeginAnon
* Struck through repros no longer work on HEAD.