syzbot
KASAN: use-after-free Read in ext4_listxattr
Status:
upstream: reported C repro on 2026/06/04 20:13
Reported-by: syzbot+e12ea4689cb4be2c2709@syzkaller.appspotmail.com
First crash: 53d, last: 13d
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Last patch testing requests (3)
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Fix bisection attempts (1)
Sample crash report:
EXT4-fs (loop2): mounted filesystem without journal. Opts: errors=remount-ro,mblk_io_submit,mblk_io_submit,resgid=0x0000000000000000,oldalloc,mblk_io_submit,nogrpid,
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_list_entries fs/ext4/xattr.c:670 [inline]
BUG: KASAN: use-after-free in ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
BUG: KASAN: use-after-free in ext4_listxattr+0x4a9/0xc60 fs/ext4/xattr.c:765
Read of size 4 at addr ffff8881104f5018 by task syz.2.17/386
CPU: 0 PID: 386 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
__dump_stack+0x21/0x24 lib/dump_stack.c:77
dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
__kasan_report mm/kasan/report.c:435 [inline]
kasan_report+0x100/0x140 mm/kasan/report.c:452
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
ext4_xattr_list_entries fs/ext4/xattr.c:670 [inline]
ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
ext4_listxattr+0x4a9/0xc60 fs/ext4/xattr.c:765
vfs_listxattr fs/xattr.c:420 [inline]
listxattr+0x28f/0x300 fs/xattr.c:715
path_listxattr+0xe1/0x1b0 fs/xattr.c:739
__do_sys_listxattr fs/xattr.c:751 [inline]
__se_sys_listxattr fs/xattr.c:748 [inline]
__x64_sys_listxattr+0x80/0x90 fs/xattr.c:748
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f20b23e5e59
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:00007ffe87625a88 EFLAGS: 00000246 ORIG_RAX: 00000000000000c2
RAX: ffffffffffffffda RBX: 00007f20b266dfa0 RCX: 00007f20b23e5e59
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000200000000140
RBP: 00007f20b247be6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f20b266dfac R14: 00007f20b266dfa0 R15: 00007f20b266dfa0
Allocated by task 95:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:430 [inline]
__kasan_slab_alloc+0xb7/0xe0 mm/kasan/common.c:463
kasan_slab_alloc include/linux/kasan.h:244 [inline]
slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
slab_alloc_node mm/slub.c:2952 [inline]
slab_alloc mm/slub.c:2960 [inline]
kmem_cache_alloc+0x15a/0x2d0 mm/slub.c:2965
kmem_cache_alloc_node include/linux/slab.h:426 [inline]
__alloc_skb+0x9e/0x520 net/core/skbuff.c:200
alloc_skb include/linux/skbuff.h:1126 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
netlink_sendmsg+0x693/0xb70 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2377
___sys_sendmsg+0x236/0x2e0 net/socket.c:2431
__sys_sendmsg net/socket.c:2460 [inline]
__do_sys_sendmsg net/socket.c:2469 [inline]
__se_sys_sendmsg net/socket.c:2467 [inline]
__x64_sys_sendmsg+0x201/0x2d0 net/socket.c:2467
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
The buggy address belongs to the object at ffff8881104f5000
which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 24 bytes inside of
248-byte region [ffff8881104f5000, ffff8881104f50f8)
The buggy address belongs to the page:
page:ffffea0004413d40 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881104f5140 pfn:0x1104f5
flags: 0x4000000000000200(slab)
raw: 4000000000000200 ffffea00043d5c48 ffffea000443da08 ffff888107d93200
raw: ffff8881104f5140 00000000000c0000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 95, ts 5305992921, free_ts 0
set_page_owner include/linux/page_owner.h:35 [inline]
post_alloc_hook mm/page_alloc.c:2456 [inline]
prep_new_page+0x176/0x190 mm/page_alloc.c:2462
get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
__alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
alloc_slab_page mm/slub.c:-1 [inline]
allocate_slab mm/slub.c:1813 [inline]
new_slab+0x84/0x3f0 mm/slub.c:1874
new_slab_objects mm/slub.c:2632 [inline]
___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
__slab_alloc+0x63/0xa0 mm/slub.c:2836
slab_alloc_node mm/slub.c:2918 [inline]
slab_alloc mm/slub.c:2960 [inline]
kmem_cache_alloc+0x1a4/0x2d0 mm/slub.c:2965
kmem_cache_alloc_node include/linux/slab.h:426 [inline]
__alloc_skb+0x9e/0x520 net/core/skbuff.c:200
alloc_skb include/linux/skbuff.h:1126 [inline]
netlink_alloc_large_skb net/netlink/af_netlink.c:1178 [inline]
netlink_sendmsg+0x693/0xb70 net/netlink/af_netlink.c:1894
sock_sendmsg_nosec net/socket.c:652 [inline]
__sock_sendmsg net/socket.c:664 [inline]
____sys_sendmsg+0x5be/0x8f0 net/socket.c:2377
___sys_sendmsg+0x236/0x2e0 net/socket.c:2431
__sys_sendmsg net/socket.c:2460 [inline]
__do_sys_sendmsg net/socket.c:2469 [inline]
__se_sys_sendmsg net/socket.c:2467 [inline]
__x64_sys_sendmsg+0x201/0x2d0 net/socket.c:2467
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
page_owner free stack trace missing
Memory state around the buggy address:
ffff8881104f4f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8881104f4f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8881104f5000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881104f5080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
ffff8881104f5100: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
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* Struck through repros no longer work on HEAD.