KASAN: use-after-free Read in lmWriteRecord

Status: upstream: reported on 2026/08/09 01:11
Reported-by: syzbot+78b566c4f7dc432513b1@syzkaller.appspotmail.com
First crash: 8d15h, last: 8d15h
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: slab-out-of-bounds Read in lmWriteRecord 19 2 233d 262d 0/3 auto-obsoleted due to no activity on 2026/04/06 10:48
linux-5.15 KASAN: slab-out-of-bounds Read in lmWriteRecord origin:upstream 19 syz, C error 5 53d 214d 0/3 upstream: reported C repro on 2026/01/15 07:37
linux-5.15 general protection fault in lmWriteRecord 2 1 577d 577d 0/3 auto-obsoleted due to no activity on 2025/04/26 22:02

Sample crash report:
loop7: detected capacity change from 0 to 32768
==================================================================
BUG: KASAN: use-after-free in lmWriteRecord+0x3e0/0x1698 fs/jfs/jfs_logmgr.c:425
Read of size 32 at addr ffff0000ea26ce00 by task syz.7.459/6916

CPU: 1 PID: 6916 Comm: syz.7.459 Tainted: G   M               syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/02/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x258/0x290 mm/kasan/generic.c:189
 memcpy+0x48/0x90 mm/kasan/shadow.c:65
 lmWriteRecord+0x3e0/0x1698 fs/jfs/jfs_logmgr.c:425
 lmLog+0x558/0x83c fs/jfs/jfs_logmgr.c:314
 dtLog fs/jfs/jfs_txnmgr.c:1619 [inline]
 txLog fs/jfs/jfs_txnmgr.c:1401 [inline]
 txCommit+0x14ec/0x3d34 fs/jfs/jfs_txnmgr.c:1265
 jfs_mkdir+0x730/0x8fc fs/jfs/namei.c:290
 vfs_mkdir+0x314/0x4d8 fs/namei.c:4114
 do_mkdirat+0x1b8/0x3ec fs/namei.c:4139
 __do_sys_mkdirat fs/namei.c:4154 [inline]
 __se_sys_mkdirat fs/namei.c:4152 [inline]
 __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4152
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Allocated by task 6895:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 __kasan_slab_alloc+0x70/0x88 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x74/0x430 mm/slab.h:737
 kmem_cache_alloc_bulk+0x420/0x4e8 mm/slub.c:3880
 mt_alloc_bulk lib/maple_tree.c:159 [inline]
 mas_alloc_nodes+0x3b4/0x758 lib/maple_tree.c:1301
 mas_node_count_gfp lib/maple_tree.c:1361 [inline]
 mas_preallocate+0x13c/0x310 lib/maple_tree.c:5809
 do_mas_align_munmap+0x1c0/0xf28 mm/mmap.c:2453
 do_mas_munmap mm/mmap.c:2650 [inline]
 __mmap_region mm/mmap.c:2698 [inline]
 mmap_region+0x6a0/0x1860 mm/mmap.c:2916
 do_mmap+0xa64/0x1210 mm/mmap.c:1436
 vm_mmap_pgoff+0x194/0x298 mm/util.c:520
 ksys_mmap_pgoff+0x364/0x5a0 mm/mmap.c:1482
 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
 __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
 __arm64_sys_mmap+0x108/0x120 arch/arm64/kernel/sys.c:21
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Freed by task 6895:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_free_info+0x38/0x5c mm/kasan/generic.c:516
 ____kasan_slab_free+0x148/0x1b0 mm/kasan/common.c:237
 __kasan_slab_free+0x18/0x28 mm/kasan/common.c:245
 kasan_slab_free include/linux/kasan.h:177 [inline]
 slab_free_hook mm/slub.c:1729 [inline]
 slab_free_freelist_hook+0x16c/0x1e8 mm/slub.c:1755
 slab_free mm/slub.c:3687 [inline]
 kmem_cache_free_bulk+0x340/0x3d4 mm/slub.c:3805
 mt_free_bulk lib/maple_tree.c:164 [inline]
 mas_destroy+0x1c30/0x232c lib/maple_tree.c:5864
 mas_store_prealloc+0x288/0x358 lib/maple_tree.c:5792
 do_mas_align_munmap+0x940/0xf28 mm/mmap.c:2574
 do_mas_munmap mm/mmap.c:2650 [inline]
 __mmap_region mm/mmap.c:2698 [inline]
 mmap_region+0x6a0/0x1860 mm/mmap.c:2916
 do_mmap+0xa64/0x1210 mm/mmap.c:1436
 vm_mmap_pgoff+0x194/0x298 mm/util.c:520
 ksys_mmap_pgoff+0x364/0x5a0 mm/mmap.c:1482
 __do_sys_mmap arch/arm64/kernel/sys.c:28 [inline]
 __se_sys_mmap arch/arm64/kernel/sys.c:21 [inline]
 __arm64_sys_mmap+0x108/0x120 arch/arm64/kernel/sys.c:21
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000ea26ce00
 which belongs to the cache maple_node of size 256
The buggy address is located 0 bytes inside of
 256-byte region [ffff0000ea26ce00, ffff0000ea26cf00)

The buggy address belongs to the physical page:
page:0000000021d7f1ee refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x12a26c
head:0000000021d7f1ee order:1 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 fffffc000340e680 dead000000000002 ffff0000c000d680
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000ea26cd00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000ea26cd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff0000ea26ce00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff0000ea26ce80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff0000ea26cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/09 01:10 linux-6.1.y e4f7d8be268e 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: use-after-free Read in lmWriteRecord
* Struck through repros no longer work on HEAD.