KASAN: use-after-free Read in ext4_xattr_ibody_get

Status: upstream: reported C repro on 2026/06/02 13:41
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+51dbb0b06cc568475c91@syzkaller.appspotmail.com
First crash: 55d, last: 11d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/06/30 lts (merge base) 64ee49df839f C [report] lost connection to test machine
2026/06/30 upstream (ToT) dc59e4fea9d8 C [report] lost connection to test machine
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get 19 C 10 11d 154d 0/2 upstream: reported C repro on 2026/02/24 05:00
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/06/17 19:40 18m retest repro android13-5.15-lts log

Sample crash report:
loop2: detected capacity change from 0 to 1024
EXT4-fs (loop2): mounted filesystem without journal. Opts: block_validity,errors=remount-ro,sysvgroups,norecovery,debug_want_extra_isize=0x0000000000000080,grpjquota=,nogrpid,noauto_da_alloc,norecovery,. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in xattr_find_entry fs/ext4/xattr.c:294 [inline]
BUG: KASAN: use-after-free in ext4_xattr_ibody_get+0x606/0x670 fs/ext4/xattr.c:601
Read of size 4 at addr ffff888112625004 by task syz.2.20/383

CPU: 0 PID: 383 Comm: syz.2.20 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 xattr_find_entry fs/ext4/xattr.c:294 [inline]
 ext4_xattr_ibody_get+0x606/0x670 fs/ext4/xattr.c:601
 ext4_xattr_get+0x116/0x830 fs/ext4/xattr.c:655
 ext4_get_acl+0x85/0x6c0 fs/ext4/acl.c:165
 get_acl+0x161/0x270 fs/posix_acl.c:153
 posix_acl_chmod+0xe9/0x250 fs/posix_acl.c:602
 ext4_setattr+0xb6b/0x1b10 fs/ext4/inode.c:5672
 notify_change+0xc30/0xf40 fs/attr.c:505
 chmod_common+0x21a/0x3c0 fs/open.c:583
 do_fchmodat+0xd4/0x1a0 fs/open.c:622
 __do_sys_fchmodat fs/open.c:635 [inline]
 __se_sys_fchmodat fs/open.c:632 [inline]
 __x64_sys_fchmodat+0x7b/0x90 fs/open.c:632
 x64_sys_call+0x1b7/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:269
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f441ec48e99
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:00007ffc608c93c8 EFLAGS: 00000246 ORIG_RAX: 000000000000010c
RAX: ffffffffffffffda RBX: 00007f441eed0fa0 RCX: 00007f441ec48e99
RDX: 00000000ffffff50 RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007f441ecdeeaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f441eed0fac R14: 00007f441eed0fa0 R15: 00007f441eed0fa0
 </TASK>

Allocated by task 115:
 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:433 [inline]
 __kasan_slab_alloc+0xb7/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3245 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
 kmem_cache_alloc_node include/linux/slab.h:492 [inline]
 __alloc_skb+0xe4/0x730 net/core/skbuff.c:416
 alloc_skb include/linux/skbuff.h:1183 [inline]
 alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x335/0x5a0 lib/kobject_uevent.c:409
 kobject_uevent_env+0x52b/0x700 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
 uevent_store+0x25/0x60 drivers/base/core.c:2438
 dev_attr_store+0x5e/0x80 drivers/base/core.c:2136
 sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:139
 kernfs_fop_write_iter+0x2bd/0x400 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2212 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x831/0xfd0 fs/read_write.c:594
 ksys_write+0x14a/0x260 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x8ef/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

The buggy address belongs to the object at ffff888112625000
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 4 bytes inside of
 248-byte region [ffff888112625000, ffff8881126250f8)
The buggy address belongs to the page:
page:ffffea0004498940 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888112625000 pfn:0x112625
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 ffffea0004498848 ffffea0004498988 ffff8881081aaa80
raw: ffff888112625000 00000000000c0006 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 115, ts 4711020847, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
 kmem_cache_alloc_node include/linux/slab.h:492 [inline]
 __alloc_skb+0xe4/0x730 net/core/skbuff.c:416
 alloc_skb include/linux/skbuff.h:1183 [inline]
 alloc_uevent_skb+0x85/0x240 lib/kobject_uevent.c:290
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x335/0x5a0 lib/kobject_uevent.c:409
 kobject_uevent_env+0x52b/0x700 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x457/0x940 lib/kobject_uevent.c:208
 uevent_store+0x25/0x60 drivers/base/core.c:2438
 dev_attr_store+0x5e/0x80 drivers/base/core.c:2136
 sysfs_kf_write+0x129/0x150 fs/sysfs/file.c:139
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888112624f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888112624f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888112625000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888112625080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
 ffff888112625100: 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.2.20: corrupted xattr entries
EXT4-fs (loop2): Remounting filesystem read-only

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/17 07:44 android13-5.15-lts 31c263582f4e 7f27c57a .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/07/17 06:44 android13-5.15-lts 31c263582f4e 7f27c57a .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/07/17 06:05 android13-5.15-lts 31c263582f4e 7f27c57a .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/06/26 22:37 android13-5.15-lts c85054db4618 fb92f11c .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-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/06/26 22:05 android13-5.15-lts c85054db4618 fb92f11c .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-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/06/26 20:57 android13-5.15-lts c85054db4618 fb92f11c .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-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/06/02 13:40 android13-5.15-lts 8969ee93a483 62fe1528 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/06/26 21:23 android13-5.15-lts c85054db4618 fb92f11c .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1 (clean fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get
* Struck through repros no longer work on HEAD.