[v6.1] KASAN: slab-out-of-bounds Read in txAllocPMap

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 228da13e907e Linux 6.1.175
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16ce14ae580000
kernel config: https://syzkaller.appspot.com/x/.config?x=29caf4bae4b0566f
dashboard link: https://syzkaller.appspot.com/bug?extid=5b48eddedc23a0440a22
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf27a408696a/disk-228da13e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/264d4943ab43/vmlinux-228da13e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a499b0d2a133/Image-228da13e.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b48ed...@syzkaller.appspotmail.com

blkno = 7400766461, nblocks = 61625f
ERROR: (device loop3): dbUpdatePMap: blocks are outside the map
==================================================================
BUG: KASAN: slab-out-of-bounds in txAllocPMap+0x448/0x5d4 fs/jfs/jfs_txnmgr.c:2412
Read of size 1 at addr ffff0000cff79010 by task jfsCommit/94

CPU: 1 PID: 94 Comm: jfsCommit Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call trace:
dump_backtrace+0x1c0/0x1ec 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
__asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
txAllocPMap+0x448/0x5d4 fs/jfs/jfs_txnmgr.c:2412
txUpdateMap+0x240/0x794 fs/jfs/jfs_txnmgr.c:2309
txLazyCommit fs/jfs/jfs_txnmgr.c:2665 [inline]
jfs_lazycommit+0x354/0x908 fs/jfs/jfs_txnmgr.c:2733
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Allocated by task 6179:
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_kmalloc mm/kasan/common.c:375 [inline]
__kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
kasan_kmalloc include/linux/kasan.h:211 [inline]
__do_kmalloc_node mm/slab_common.c:936 [inline]
__kmalloc_node_track_caller+0xe0/0x16c mm/slab_common.c:956
kstrdup mm/util.c:61 [inline]
kstrdup_const+0x90/0xdc mm/util.c:84
__kernfs_new_node+0xb0/0x5f4 fs/kernfs/dir.c:610
kernfs_new_node+0x11c/0x22c fs/kernfs/dir.c:690
kernfs_create_dir_ns+0x58/0x12c fs/kernfs/dir.c:1046
sysfs_create_dir_ns+0x120/0x264 fs/sysfs/dir.c:59
create_dir lib/kobject.c:63 [inline]
kobject_add_internal+0x598/0xb08 lib/kobject.c:231
kobject_add_varg lib/kobject.c:366 [inline]
kobject_add+0x140/0x20c lib/kobject.c:418
device_add+0x3f8/0xefc drivers/base/core.c:3632
netdev_register_kobject+0x164/0x2e0 net/core/net-sysfs.c:2013
register_netdevice+0xf1c/0x1614 net/core/dev.c:10243
veth_newlink+0x490/0xaa0 drivers/net/veth.c:1725
rtnl_newlink_create net/core/rtnetlink.c:3428 [inline]
__rtnl_newlink net/core/rtnetlink.c:3648 [inline]
rtnl_newlink+0x1050/0x1a54 net/core/rtnetlink.c:3661
rtnetlink_rcv_msg+0x698/0xcdc net/core/rtnetlink.c:6158
netlink_rcv_skb+0x218/0x3e8 net/netlink/af_netlink.c:2511
rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6176
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x60c/0x814 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6f4/0x9c0 net/netlink/af_netlink.c:1872
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x324/0x440 net/socket.c:2152
__do_sys_sendto net/socket.c:2164 [inline]
__se_sys_sendto net/socket.c:2160 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2160
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 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 ffff0000cff79000
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 16 bytes inside of
128-byte region [ffff0000cff79000, ffff0000cff79080)

The buggy address belongs to the physical page:
page:00000000a4271a1b refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10ff79
flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000200 0000000000000000 dead000000000122 ffff0000c0002300
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff0000cff78f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff0000cff78f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000cff79000: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff0000cff79080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff0000cff79100: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
blkno = 7400766461, nblocks = 61625f
ERROR: (device loop3): dbUpdatePMap: blocks are outside the map

blkno = 7461625f6f, nblocks = 5f3168
ERROR: (device loop3): dbUpdatePMap: blocks are outside the map



---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 228da13e907e Linux 6.1.175
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=17e2b4ae580000

kernel config: https://syzkaller.appspot.com/x/.config?x=29caf4bae4b0566f
dashboard link: https://syzkaller.appspot.com/bug?extid=5b48eddedc23a0440a22
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1116f5ee580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1755c4ae580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/bf27a408696a/disk-228da13e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/264d4943ab43/vmlinux-228da13e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a499b0d2a133/Image-228da13e.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/0b8888fbee3b/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=174c0b7a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b48ed...@syzkaller.appspotmail.com

blkno = 8100000000, nblocks = 240152
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

==================================================================
BUG: KASAN: slab-out-of-bounds in txAllocPMap+0x448/0x5d4 fs/jfs/jfs_txnmgr.c:2412

Read of size 1 at addr ffff0000c457e0b0 by task jfsCommit/91

CPU: 1 PID: 91 Comm: jfsCommit Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/02/2026

Call trace:
dump_backtrace+0x1c0/0x1ec 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
__asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
txAllocPMap+0x448/0x5d4 fs/jfs/jfs_txnmgr.c:2412
txUpdateMap+0x240/0x794 fs/jfs/jfs_txnmgr.c:2309
txLazyCommit fs/jfs/jfs_txnmgr.c:2665 [inline]
jfs_lazycommit+0x354/0x908 fs/jfs/jfs_txnmgr.c:2733
kthread+0x250/0x2d8 kernel/kthread.c:376
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:850

Allocated by task 4463:

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
slab_alloc_node mm/slub.c:3359 [inline]
slab_alloc mm/slub.c:3367 [inline]
__kmem_cache_alloc_lru mm/slub.c:3374 [inline]
kmem_cache_alloc+0x22c/0x308 mm/slub.c:3383
kmem_cache_zalloc include/linux/slab.h:689 [inline]
__kernfs_new_node+0xec/0x5f4 fs/kernfs/dir.c:614
kernfs_new_node+0x11c/0x22c fs/kernfs/dir.c:690
__kernfs_create_file+0x60/0x2d4 fs/kernfs/file.c:1068
sysfs_add_file_mode_ns+0x1d8/0x294 fs/sysfs/file.c:294
create_files fs/sysfs/group.c:64 [inline]
internal_create_group+0x3e0/0xad4 fs/sysfs/group.c:148
internal_create_groups fs/sysfs/group.c:188 [inline]
sysfs_create_groups+0x60/0x134 fs/sysfs/group.c:214
device_add_groups drivers/base/core.c:2752 [inline]
device_add_attrs+0x178/0x6f4 drivers/base/core.c:2911
device_add+0x5e4/0xefc drivers/base/core.c:3648

netdev_register_kobject+0x164/0x2e0 net/core/net-sysfs.c:2013
register_netdevice+0xf1c/0x1614 net/core/dev.c:10243

br_dev_newlink+0x34/0x10c net/bridge/br_netlink.c:1499

rtnl_newlink_create net/core/rtnetlink.c:3428 [inline]
__rtnl_newlink net/core/rtnetlink.c:3648 [inline]
rtnl_newlink+0x1050/0x1a54 net/core/rtnetlink.c:3661
rtnetlink_rcv_msg+0x698/0xcdc net/core/rtnetlink.c:6158
netlink_rcv_skb+0x218/0x3e8 net/netlink/af_netlink.c:2511
rtnetlink_rcv+0x28/0x38 net/core/rtnetlink.c:6176
netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
netlink_unicast+0x60c/0x814 net/netlink/af_netlink.c:1344
netlink_sendmsg+0x6f4/0x9c0 net/netlink/af_netlink.c:1872
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x324/0x440 net/socket.c:2152
__do_sys_sendto net/socket.c:2164 [inline]
__se_sys_sendto net/socket.c:2160 [inline]
__arm64_sys_sendto+0xd8/0xf8 net/socket.c:2160
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 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 ffff0000c457e000
which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 8 bytes to the right of
168-byte region [ffff0000c457e000, ffff0000c457e0a8)

The buggy address belongs to the physical page:

page:00000000303e7b6d refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10457e

flags: 0x5ffc00000000200(slab|node=0|zone=2|lastcpupid=0x7ff)

raw: 05ffc00000000200 0000000000000000 dead000000000122 ffff0000c03dca80
raw: 0000000000000000 0000000000110011 00000001ffffffff 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff0000c457df80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff0000c457e000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000c457e080: 00 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00
^
ffff0000c457e100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff0000c457e180: 00 00 fc fc fc fc fc fc fc fc 00 00 00 00 00 00
==================================================================
blkno = d8ffff0000, nblocks = d4f780
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = dcffff0000, nblocks = a64680
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 4100000000, nblocks = ed0011
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 16ffff8000, nblocks = 877ff8
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 11ffff8000, nblocks = c97420
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 8100000000, nblocks = a40152
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 16ffff8000, nblocks = 8780b8
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 11ffff8000, nblocks = c97420
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map

blkno = 8100000000, nblocks = 240152
ERROR: (device loop1): dbUpdatePMap: blocks are outside the map



---
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