KASAN: use-after-free Read in xattr_find_entry

Status: upstream: reported C repro on 2026/06/22 02:11
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+8dc2a17ad14a884441dd@syzkaller.appspotmail.com
First crash: 48d, last: 20d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/07/21 lts (merge base) 4fd016be1e49 C [report] lost connection to test machine
2026/07/21 upstream (ToT) 248951ddc14d C [report] lost connection to test machine
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in xattr_find_entry ext4 19 2 291d 289d 0/29 auto-obsoleted due to no activity on 2026/01/20 09:16
upstream KASAN: use-after-free Read in xattr_find_entry (2) prio:high ext4 19 syz, C error error 3 157d 167d 0/29 upstream: reported C repro on 2026/02/23 00:12
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/07/13 15:06 15m retest repro android14-6.1 log

Sample crash report:
loop2: detected capacity change from 0 to 1024
EXT4-fs (loop2): mounted filesystem without journal. Quota mode: writeback.
==================================================================
BUG: KASAN: use-after-free in xattr_find_entry+0x2f5/0x300 fs/ext4/xattr.c:294
Read of size 4 at addr ffff888114d48004 by task syz.2.17/374

CPU: 0 PID: 374 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 xattr_find_entry+0x2f5/0x300 fs/ext4/xattr.c:294
 ext4_xattr_ibody_get+0x245/0x4d0 fs/ext4/xattr.c:601
 ext4_xattr_get+0x122/0x650 fs/ext4/xattr.c:655
 ext4_get_acl+0x85/0x6c0 fs/ext4/acl.c:165
 get_acl+0x16f/0x280 fs/posix_acl.c:153
 posix_acl_chmod+0xe9/0x260 fs/posix_acl.c:602
 ext4_setattr+0xd4e/0x1c80 fs/ext4/inode.c:5693
 notify_change+0xd33/0x1030 fs/attr.c:499
 chmod_common+0x21a/0x3c0 fs/open.c:607
 do_fchmodat+0xd4/0x1a0 fs/open.c:646
 __do_sys_chmod fs/open.c:664 [inline]
 __se_sys_chmod fs/open.c:662 [inline]
 __x64_sys_chmod+0x60/0x70 fs/open.c:662
 x64_sys_call+0x760/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:91
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f737019de99
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:00007ffe43762a08 EFLAGS: 00000246 ORIG_RAX: 000000000000005a
RAX: ffffffffffffffda RBX: 00007f7370425fa0 RCX: 00007f737019de99
RDX: 0000000000000000 RSI: 000000000000023f RDI: 0000200000000180
RBP: 00007f7370233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7370425fac R14: 00007f7370425fa0 R15: 00007f7370425fa0
 </TASK>

Allocated by task 117:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_alloc_info+0x1f/0x30 mm/kasan/generic.c:505
 __kasan_slab_alloc+0x72/0x80 mm/kasan/common.c:334
 kasan_slab_alloc include/linux/kasan.h:202 [inline]
 slab_post_alloc_hook+0x4f/0x2d0 mm/slab.h:768
 slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc+0x166/0x320 mm/slub.c:3408
 skb_clone+0x1e8/0x380 net/core/skbuff.c:1663
 do_one_broadcast net/netlink/af_netlink.c:1454 [inline]
 netlink_broadcast+0x698/0x1170 net/netlink/af_netlink.c:1520
 uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
 kobject_uevent_net_broadcast+0x3cb/0x5b0 lib/kobject_uevent.c:409
 kobject_uevent_env+0x541/0x720 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
 uevent_store+0x25/0x70 drivers/base/core.c:2690
 dev_attr_store+0x6c/0x90 drivers/base/core.c:2389
 sysfs_kf_write+0x137/0x150 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x307/0x470 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x5ef/0xd00 fs/read_write.c:584
 ksys_write+0x14a/0x260 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 103:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:242
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:250
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 kmem_cache_free+0x12d/0x300 mm/slub.c:3737
 kfree_skbmem+0x10c/0x180 net/core/skbuff.c:-1
 __kfree_skb net/core/skbuff.c:874 [inline]
 consume_skb+0xb3/0x1f0 net/core/skbuff.c:1038
 skb_free_datagram+0x15/0x20 net/core/datagram.c:322
 netlink_recvmsg+0x5e3/0xe00 net/netlink/af_netlink.c:1951
 ____sys_recvmsg+0x2d6/0x5c0 net/socket.c:-1
 ___sys_recvmsg+0x210/0x590 net/socket.c:2769
 __sys_recvmsg net/socket.c:2799 [inline]
 __do_sys_recvmsg net/socket.c:2809 [inline]
 __se_sys_recvmsg net/socket.c:2806 [inline]
 __x64_sys_recvmsg+0x20a/0x2e0 net/socket.c:2806
 x64_sys_call+0x75/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:48
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888114d48000
 which belongs to the cache skbuff_head_cache of size 256
The buggy address is located 4 bytes inside of
 256-byte region [ffff888114d48000, ffff888114d48100)

The buggy address belongs to the physical page:
page:ffffea0004535200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x114d48
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 ffffea00045352c0 dead000000000003 ffff888108858a80
raw: 0000000000000000 00000000000c000c 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 117, tgid 117 (udevadm), ts 4169240235, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2672
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2679
 get_page_from_freelist+0x2ca9/0x2d20 mm/page_alloc.c:4586
 __alloc_pages+0x1fa/0x610 mm/page_alloc.c:5930
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3e0 mm/slub.c:2020
 ___slab_alloc+0x70f/0xb70 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 slab_alloc mm/slub.c:3392 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3399 [inline]
 kmem_cache_alloc+0x1a8/0x320 mm/slub.c:3408
 skb_clone+0x1e8/0x380 net/core/skbuff.c:1663
 do_one_broadcast net/netlink/af_netlink.c:1454 [inline]
 netlink_broadcast+0x698/0x1170 net/netlink/af_netlink.c:1520
 uevent_net_broadcast_untagged lib/kobject_uevent.c:331 [inline]
 kobject_uevent_net_broadcast+0x3cb/0x5b0 lib/kobject_uevent.c:409
 kobject_uevent_env+0x541/0x720 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
 uevent_store+0x25/0x70 drivers/base/core.c:2690
 dev_attr_store+0x6c/0x90 drivers/base/core.c:2389
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888114d47f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888114d47f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888114d48000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888114d48080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888114d48100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================
EXT4-fs error (device loop2): xattr_find_entry:297: inode #12: comm syz.2.17: corrupted xattr entries

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/20 06:03 android14-6.1 c7e15f0bdc49 72524a66 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in xattr_find_entry
2026/07/20 05:20 android14-6.1 c7e15f0bdc49 72524a66 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in xattr_find_entry
2026/07/20 04:39 android14-6.1 c7e15f0bdc49 72524a66 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in xattr_find_entry
2026/07/20 04:10 android14-6.1 c7e15f0bdc49 72524a66 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in xattr_find_entry
2026/06/22 02:09 android14-6.1 72813af230c7 43bfcdb0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-6-1 KASAN: use-after-free Read in xattr_find_entry
* Struck through repros no longer work on HEAD.