KASAN: use-after-free Read in ext4_xattr_list_entries (2)

Status: upstream: reported on 2026/06/09 21:03
Subsystems: ext4
Labels: actionable prio:high
[Documentation on labels]
Reported-by: syzbot+3fbf2337de43f5581aec@syzkaller.appspotmail.com
First crash: 100d, last: 21d
✨ AI Jobs (4)
ID Workflow Result Correct Bug Created Started Finished Revision
ef33d515 repro-c Reproduced: ✅ KASAN: use-after-free Read in ext4_xattr_list_entries (2) 2026/08/07 13:51 2026/08/07 19:11 2026/08/07 21:11 e4ef95d6
3d7b2494 assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ✅ NetworkTrigger: ❌ PeripheralTrigger: ✅ RemoteTrigger: ❌ Unprivileged: ❌ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ✅ KASAN: use-after-free Read in ext4_xattr_list_entries (2) 2026/06/09 20:18 2026/06/09 20:18 2026/06/09 21:13 c36c07f6
b34af3c3 moderation Actionable: ✅ KASAN: use-after-free Read in ext4_xattr_list_entries (2) 2026/06/09 20:16 2026/06/09 20:16 2026/06/09 21:02 c36c07f6
662933c2 assessment-security 💥 KASAN: use-after-free Read in ext4_xattr_list_entries (2) 2026/06/04 00:00 2026/06/04 00:00 2026/06/04 00:00 62fe1528
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [ext4?] KASAN: use-after-free Read in ext4_xattr_list_entries (2) 0 (1) 2026/06/09 21:03
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in ext4_xattr_list_entries ext4 19 4 244d 335d 0/29 auto-obsoleted due to no activity on 2026/04/10 00:23
linux-6.1 KASAN: use-after-free Read in ext4_xattr_list_entries 19 syz, C error 15 211d 236d 0/3 upstream: reported C repro on 2026/01/18 01:47
android-6-1 KASAN: use-after-free Read in ext4_xattr_list_entries 19 syz, C inconclusive 6 58d 58d 0/2 upstream: reported C repro on 2026/07/14 23:26

Sample crash report:
loop0: detected capacity change from 0 to 2048
EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.
loop0: detected capacity change from 2048 to 64
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_list_entries+0x302/0x3d0 fs/ext4/xattr.c:724
Read of size 4 at addr ffff888051f5f014 by task syz.0.0/5321

CPU: 0 UID: 0 PID: 5321 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 ext4_xattr_list_entries+0x302/0x3d0 fs/ext4/xattr.c:724
 ext4_xattr_ibody_list fs/ext4/xattr.c:793 [inline]
 ext4_listxattr+0x229/0x680 fs/ext4/xattr.c:818
 vfs_listxattr fs/xattr.c:516 [inline]
 listxattr+0x19d/0x380 fs/xattr.c:941
 filename_listxattr fs/xattr.c:974 [inline]
 path_listxattrat+0x1a3/0x3f0 fs/xattr.c:1001
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdc9919e0d9
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:00007fdc99f84fe8 EFLAGS: 00000246 ORIG_RAX: 00000000000000c2
RAX: ffffffffffffffda RBX: 00007fdc99425fa0 RCX: 00007fdc9919e0d9
RDX: 0000000000000084 RSI: 0000200000000180 RDI: 0000200000000080
RBP: 00007fdc99235024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdc99426038 R14: 00007fdc99425fa0 R15: 00007ffe5322df58
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x51f5f
flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff00000000000 ffffea000147d808 ffffea000147d548 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff888051f5ef00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888051f5ef80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888051f5f000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff888051f5f080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888051f5f100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/20 16:26 upstream a4ff2be345d0 1e72964b .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/08/04 04:43 upstream 848acc8ffe1b 9451e17e .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/07/24 02:44 upstream d326f83e819c 544adce9 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/07/05 15:08 upstream 7404ce516372 fcece630 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/06/07 13:40 upstream 8e65320d91cd cc095639 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/06/02 20:37 upstream 6f3ed7fec72f 62fe1528 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: use-after-free Read in ext4_xattr_list_entries
2026/07/25 05:36 upstream e2a936998ab2 492bab15 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-use-after-free Read in ext4_xattr_list_entries
* Struck through repros no longer work on HEAD.