[v6.6] KASAN: use-after-free Read in leaf_paste_entries (2)

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syzbot

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Nov 10, 2025, 5:16:25 AM (11 days ago) Nov 10
to syzkaller...@googlegroups.com
Hello,

syzbot found the following issue on:

HEAD commit: 0a805b6ea8cd Linux 6.6.116
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16b7260a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=9145cb498df875fd6176
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/13874446b4b2/disk-0a805b6e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/69a5e59e1ade/vmlinux-0a805b6e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/322c0711f976/bzImage-0a805b6e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9145cb...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in leaf_paste_entries+0x51c/0x1110 fs/reiserfs/lbalance.c:1362
Read of size 2 at addr ffff88807425a008 by task syz.0.300/7501

CPU: 1 PID: 7501 Comm: syz.0.300 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
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
leaf_paste_entries+0x51c/0x1110 fs/reiserfs/lbalance.c:1362
leaf_copy_dir_entries+0x699/0x990 fs/reiserfs/lbalance.c:119
leaf_copy_boundary_item+0xb90/0x2180 fs/reiserfs/lbalance.c:168
leaf_copy_items fs/reiserfs/lbalance.c:551 [inline]
leaf_move_items+0x8b5/0xe90 fs/reiserfs/lbalance.c:726
leaf_shift_left+0xbd/0x450 fs/reiserfs/lbalance.c:750
balance_leaf_when_delete_left fs/reiserfs/do_balan.c:194 [inline]
balance_leaf_when_delete fs/reiserfs/do_balan.c:272 [inline]
balance_leaf+0x1dc1/0x10da0 fs/reiserfs/do_balan.c:1393
do_balance+0x2fe/0x940 fs/reiserfs/do_balan.c:1888
reiserfs_cut_from_item+0x13b2/0x1f10 fs/reiserfs/stree.c:1836
reiserfs_do_truncate+0xa3d/0x1340 fs/reiserfs/stree.c:1971
reiserfs_truncate_file+0x37a/0x7c0 fs/reiserfs/inode.c:2306
reiserfs_setattr+0xc0c/0x11a0 fs/reiserfs/inode.c:3392
notify_change+0xb0d/0xe10 fs/attr.c:499
do_truncate+0x19b/0x220 fs/open.c:66
handle_truncate fs/namei.c:3299 [inline]
do_open fs/namei.c:3644 [inline]
path_openat+0x298c/0x3190 fs/namei.c:3797
do_filp_open+0x1c5/0x3d0 fs/namei.c:3824
do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
do_sys_open fs/open.c:1434 [inline]
__do_sys_openat fs/open.c:1450 [inline]
__se_sys_openat fs/open.c:1445 [inline]
__x64_sys_openat+0x139/0x160 fs/open.c:1445
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: 0033:0x7f132518f6c9
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:00007f1325fc1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f13253e6090 RCX: 00007f132518f6c9
RDX: 000000000000275a RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007f1325211f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f13253e6128 R14: 00007f13253e6090 R15: 00007ffe18bd5ca8
</TASK>

The buggy address belongs to the physical page:
page:ffffea0001d09680 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x7425a
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000000 ffffea0001d096c8 ffffea0001aded48 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 7483, tgid 7481 (syz.2.302), ts 268657155284, free_ts 269987925533
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
__folio_alloc+0x10/0x20 mm/page_alloc.c:4489
vma_alloc_folio+0x47a/0x8f0 mm/mempolicy.c:2242
shmem_alloc_folio+0x179/0x230 mm/shmem.c:1680
shmem_alloc_and_acct_folio+0x189/0x630 mm/shmem.c:1705
shmem_get_folio_gfp+0xcde/0x2ac0 mm/shmem.c:2042
shmem_fault+0x1b6/0x7f0 mm/shmem.c:2249
__do_fault+0x13b/0x4e0 mm/memory.c:4243
do_read_fault mm/memory.c:4616 [inline]
do_fault mm/memory.c:4753 [inline]
do_pte_missing mm/memory.c:3688 [inline]
handle_pte_fault mm/memory.c:5025 [inline]
__handle_mm_fault mm/memory.c:5166 [inline]
handle_mm_fault+0x3886/0x4920 mm/memory.c:5331
faultin_page mm/gup.c:868 [inline]
__get_user_pages+0x5ea/0x1470 mm/gup.c:1167
populate_vma_page_range+0x2b6/0x370 mm/gup.c:1593
__mm_populate+0x24c/0x380 mm/gup.c:1696
mm_populate include/linux/mm.h:3383 [inline]
vm_mmap_pgoff+0x2e7/0x400 mm/util.c:561
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page_list+0xbe/0x860 mm/page_alloc.c:2475
release_pages+0x1fa0/0x2220 mm/swap.c:1022
__folio_batch_release+0x71/0xe0 mm/swap.c:1042
folio_batch_release include/linux/pagevec.h:83 [inline]
shmem_undo_range+0x5d0/0x1a40 mm/shmem.c:1027
shmem_truncate_range mm/shmem.c:1136 [inline]
shmem_evict_inode+0x273/0xa70 mm/shmem.c:1265
evict+0x486/0x870 fs/inode.c:705
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
task_work_run+0x1ce/0x250 kernel/task_work.c:239
exit_task_work include/linux/task_work.h:43 [inline]
do_exit+0x90b/0x23c0 kernel/exit.c:883
do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
get_signal+0x12fc/0x1400 kernel/signal.c:2902
arch_do_signal_or_restart+0x9c/0x7b0 arch/x86/kernel/signal.c:310

Memory state around the buggy address:
ffff888074259f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888074259f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88807425a000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff88807425a080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff88807425a100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================


---
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If the report is already addressed, let syzbot know by replying with:
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If the report is a duplicate of another one, reply with:
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If you want to undo deduplication, reply with:
#syz undup

syzbot

unread,
Nov 10, 2025, 6:04:31 AM (11 days ago) Nov 10
to syzkaller...@googlegroups.com
syzbot has found a reproducer for the following issue on:

HEAD commit: 0a805b6ea8cd Linux 6.6.116
git tree: linux-6.6.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15f3d17c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=12606d4b8832c7e4
dashboard link: https://syzkaller.appspot.com/bug?extid=9145cb498df875fd6176
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12ec30b4580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=144507cd980000
mounted in repro: https://storage.googleapis.com/syzbot-assets/a1c39a5415bc/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=104507cd980000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9145cb...@syzkaller.appspotmail.com

REISERFS (device loop0): journal params: device loop0, size 512, journal first block 18, max trans len 256, max batch 225, max commit age 30, max trans age 30
REISERFS (device loop0): checking transaction log (loop0)
REISERFS (device loop0): Using tea hash to sort names
REISERFS (device loop0): Created .reiserfs_priv - reserved for xattr storage.
==================================================================
BUG: KASAN: slab-out-of-bounds in leaf_paste_entries+0xe78/0x1110 fs/reiserfs/lbalance.c:1351
Read of size 2 at addr ffff88805e8b3f08 by task syz.0.17/5952

CPU: 0 PID: 5952 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
print_address_description mm/kasan/report.c:364 [inline]
print_report+0xac/0x220 mm/kasan/report.c:468
kasan_report+0x117/0x150 mm/kasan/report.c:581
leaf_paste_entries+0xe78/0x1110 fs/reiserfs/lbalance.c:1351
RIP: 0033:0x7fb409b8f6c9
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:00007ffc27ee8ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fb409de5fa0 RCX: 00007fb409b8f6c9
RDX: 000000000000275a RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007fb409c11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb409de5fa0 R14: 00007fb409de5fa0 R15: 0000000000000004
</TASK>

Allocated by task 5928:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
__kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
slab_alloc_node mm/slub.c:3495 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc_lru+0x115/0x2e0 mm/slub.c:3526
alloc_inode_sb include/linux/fs.h:2946 [inline]
alloc_inode fs/inode.c:263 [inline]
new_inode_pseudo+0x82/0x1d0 fs/inode.c:1049
get_pipe_inode fs/pipe.c:879 [inline]
create_pipe_files+0x51/0x700 fs/pipe.c:919
__do_pipe_flags+0x4c/0x2c0 fs/pipe.c:968
do_pipe2+0x9d/0x170 fs/pipe.c:1019
__do_sys_pipe2 fs/pipe.c:1037 [inline]
__se_sys_pipe2 fs/pipe.c:1035 [inline]
__x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1035
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

Freed by task 5928:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
kmem_cache_free+0xf8/0x280 mm/slub.c:3852
destroy_inode fs/inode.c:311 [inline]
evict+0x756/0x870 fs/inode.c:720
__dentry_kill+0x431/0x650 fs/dcache.c:611
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfe/0x1e0 fs/dcache.c:918
__fput+0x5e5/0x970 fs/file_table.c:392
__do_sys_close fs/open.c:1571 [inline]
__se_sys_close+0x15f/0x220 fs/open.c:1556
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

The buggy address belongs to the object at ffff88805e8b37b0
which belongs to the cache inode_cache of size 1168
The buggy address is located 712 bytes to the right of
allocated 1168-byte region [ffff88805e8b37b0, ffff88805e8b3c40)

The buggy address belongs to the physical page:
page:ffffea00017a2c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x5e8b0
head:ffffea00017a2c00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff8880791f5781
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888019a4da00 dead000000000122 0000000000000000
raw: 0000000000000000 00000000000c000c 00000001ffffffff ffff8880791f5781
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Reclaimable, gfp_mask 0x1d20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 5904, tgid 5904 (syz-executor), ts 89693234377, free_ts 23549062454
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
prep_new_page mm/page_alloc.c:1561 [inline]
get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
__alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
alloc_slab_page+0x5d/0x170 mm/slub.c:1881
allocate_slab mm/slub.c:2028 [inline]
new_slab+0x87/0x2e0 mm/slub.c:2081
___slab_alloc+0xc6d/0x1300 mm/slub.c:3253
__slab_alloc mm/slub.c:3339 [inline]
__slab_alloc_node mm/slub.c:3392 [inline]
slab_alloc_node mm/slub.c:3485 [inline]
slab_alloc mm/slub.c:3503 [inline]
__kmem_cache_alloc_lru mm/slub.c:3510 [inline]
kmem_cache_alloc_lru+0x1ae/0x2e0 mm/slub.c:3526
alloc_inode_sb include/linux/fs.h:2946 [inline]
alloc_inode fs/inode.c:263 [inline]
new_inode_pseudo+0x82/0x1d0 fs/inode.c:1049
new_inode+0x22/0x1b0 fs/inode.c:1075
debugfs_get_inode fs/debugfs/inode.c:72 [inline]
__debugfs_create_file+0x148/0x500 fs/debugfs/inode.c:431
nsim_udp_tunnels_info_create+0x295/0x770 drivers/net/netdevsim/udp_tunnels.c:162
nsim_init_netdevsim drivers/net/netdevsim/netdev.c:331 [inline]
nsim_create+0x35c/0x4a0 drivers/net/netdevsim/netdev.c:401
__nsim_dev_port_add+0x702/0xb00 drivers/net/netdevsim/dev.c:1393
nsim_dev_port_add_all+0x35/0xe0 drivers/net/netdevsim/dev.c:1449
nsim_drv_probe+0x884/0xb70 drivers/net/netdevsim/dev.c:1607
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x25b/0xb40 drivers/base/dd.c:658
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1154 [inline]
free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
free_contig_range+0xa1/0x160 mm/page_alloc.c:6369
destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
debug_vm_pgtable+0x3cc/0x410 mm/debug_vm_pgtable.c:1400
do_one_initcall+0x1fd/0x750 init/main.c:1250
do_initcall_level+0x137/0x1f0 init/main.c:1312
do_initcalls+0x69/0xd0 init/main.c:1328
kernel_init_freeable+0x3d2/0x570 init/main.c:1565
kernel_init+0x1d/0x1c0 init/main.c:1455
ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
ffff88805e8b3e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805e8b3e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805e8b3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff88805e8b3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88805e8b4000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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