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KASAN: use-after-free Read in ext4_xattr_ibody_get

Status: upstream: reported C repro on 2026/02/24 05:00
Reported-by: syzbot+8033bf14e2a4aa787ba6@syzkaller.appspotmail.com
First crash: 110d, last: 25d
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-15 KASAN: use-after-free Read in ext4_xattr_ibody_get 19 C 1 11d 11d 0/2 upstream: reported C repro on 2026/06/02 13:41
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/06/10 13:52 13m retest repro android13-5.10-lts log
2026/06/10 13:52 13m retest repro android13-5.10-lts log
2026/06/10 13:52 16m retest repro android13-5.10-lts log
2026/06/10 13:52 12m retest repro android13-5.10-lts log
2026/03/10 05:57 10m retest repro android13-5.10-lts report log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2026/05/09 09:52 2h12m bisect fix android13-5.10-lts OK (0) job log log
2026/04/09 06:15 1h10m bisect fix android13-5.10-lts OK (0) job log log

Sample crash report:
EXT4-fs (loop2): mounted filesystem without journal. Opts: resgid=0x000000000000ee00,bsddf,grpquota,nojournal_checksum,debug_want_extra_isize=0x0000000000000080,delalloc,nogrpid,noauto_da_alloc,stripe=0x0000000000000002,,errors=continue
==================================================================
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+0x62e/0x690 fs/ext4/xattr.c:601
Read of size 4 at addr ffff888129424004 by task syz.2.17/385

CPU: 0 PID: 385 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+0xe2/0x130 mm/kasan/report.c:452
 __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+0x62e/0x690 fs/ext4/xattr.c:601
 ext4_xattr_get+0x116/0x820 fs/ext4/xattr.c:655
 ext4_get_acl+0x6c/0x660 fs/ext4/acl.c:162
 get_acl+0x15f/0x270 fs/posix_acl.c:141
 posix_acl_chmod+0xe4/0x240 fs/posix_acl.c:565
 ext4_setattr+0xb40/0x1950 fs/ext4/inode.c:5741
 notify_change+0xab3/0xe40 fs/attr.c:410
 chmod_common+0x1e1/0x390 fs/open.c:584
 do_fchmodat+0xd4/0x1a0 fs/open.c:622
 __do_sys_chmod fs/open.c:640 [inline]
 __se_sys_chmod fs/open.c:638 [inline]
 __x64_sys_chmod+0x60/0x70 fs/open.c:638
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f700ef49e59
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:00007ffdd720b518 EFLAGS: 00000246 ORIG_RAX: 000000000000005a
RAX: ffffffffffffffda RBX: 00007f700f1c2fa0 RCX: 00007f700ef49e59
RDX: 0000000000000000 RSI: 000000000000023f RDI: 0000200000000180
RBP: 00007f700efdfd6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f700f1c2fac R14: 00007f700f1c2fa0 R15: 00007f700f1c2fa0

Allocated by task 0:
(stack is not available)

Freed by task 112:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 skb_free_head net/core/skbuff.c:606 [inline]
 skb_release_data+0x532/0x670 net/core/skbuff.c:626
 skb_release_all net/core/skbuff.c:680 [inline]
 __kfree_skb net/core/skbuff.c:694 [inline]
 consume_skb+0xab/0x1f0 net/core/skbuff.c:851
 netlink_broadcast_filtered+0x117d/0x1270 net/netlink/af_netlink.c:1530
 netlink_broadcast net/netlink/af_netlink.c:1552 [inline]
 nlmsg_multicast include/net/netlink.h:1033 [inline]
 nlmsg_notify+0xed/0x1b0 net/netlink/af_netlink.c:2546
 rtnl_notify+0x9a/0xc0 net/core/rtnetlink.c:740
 inet_netconf_notify_devconf+0x1c2/0x220 net/ipv4/devinet.c:2132
 __devinet_sysctl_unregister net/ipv4/devinet.c:2625 [inline]
 devinet_sysctl_unregister net/ipv4/devinet.c:2649 [inline]
 inetdev_destroy net/ipv4/devinet.c:326 [inline]
 inetdev_event+0x7d9/0x1040 net/ipv4/devinet.c:1612
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2054 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2066 [inline]
 call_netdevice_notifiers net/core/dev.c:2080 [inline]
 unregister_netdevice_many+0x1074/0x1a80 net/core/dev.c:10780
 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11300
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x603/0xb80 net/core/net_namespace.c:609
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13c0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the object at ffff888129424000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 4 bytes inside of
 512-byte region [ffff888129424000, ffff888129424200)
The buggy address belongs to the page:
page:ffffea0004a50900 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x129424
head:ffffea0004a50900 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100043080
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 112, ts 28072238734, free_ts 27688480456
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 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+0x2a6/0x450 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]
 __kmalloc_track_caller+0x1ec/0x320 mm/slub.c:4541
 __kmalloc_reserve net/core/skbuff.c:144 [inline]
 __alloc_skb+0xdc/0x520 net/core/skbuff.c:212
 alloc_skb include/linux/skbuff.h:1126 [inline]
 nlmsg_new include/net/netlink.h:953 [inline]
 inet6_netconf_notify_devconf+0xd6/0x190 net/ipv6/addrconf.c:579
 __addrconf_sysctl_unregister net/ipv6/addrconf.c:7097 [inline]
 addrconf_sysctl_unregister net/ipv6/addrconf.c:7121 [inline]
 addrconf_ifdown+0x1592/0x1850 net/ipv6/addrconf.c:3940
 addrconf_notify+0x3bd/0xe90 net/ipv6/addrconf.c:-1
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:410
 call_netdevice_notifiers_info net/core/dev.c:2054 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2066 [inline]
 call_netdevice_notifiers net/core/dev.c:2080 [inline]
 unregister_netdevice_many+0x1074/0x1a80 net/core/dev.c:10780
 default_device_exit_batch+0x35e/0x3c0 net/core/dev.c:11300
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x603/0xb80 net/core/net_namespace.c:609
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 free_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page mm/page_alloc.c:3391 [inline]
 free_the_page mm/page_alloc.c:5443 [inline]
 __free_pages+0x146/0x3b0 mm/page_alloc.c:5454
 __vunmap+0x86d/0x9f0 mm/vmalloc.c:2307
 __vfree mm/vmalloc.c:2356 [inline]
 vfree+0x61/0x90 mm/vmalloc.c:2387
 kcov_put kernel/kcov.c:408 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:510
 __fput+0x2fb/0x770 fs/file_table.c:281
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0xa87/0x2500 kernel/exit.c:873
 do_group_exit+0x141/0x310 kernel/exit.c:987
 get_signal+0xf7d/0x12e0 kernel/signal.c:2793
 arch_do_signal_or_restart+0xe2/0x11d0 arch/x86/kernel/signal.c:805
 handle_signal_work kernel/entry/common.c:145 [inline]
 exit_to_user_mode_loop+0xa2/0xe0 kernel/entry/common.c:169
 exit_to_user_mode_prepare+0x76/0xa0 kernel/entry/common.c:199
 syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:274
 do_syscall_64+0x3d/0x40 arch/x86/entry/common.c:56

Memory state around the buggy address:
 ffff888129423f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888129423f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888129424000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff888129424080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888129424100: fb fb fb fb fb fb fb fb fb 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 (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/20 04:25 android13-5.10-lts f5a34916f66d 0909d65f .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-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/05/20 03:54 android13-5.10-lts f5a34916f66d 0909d65f .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-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/05/20 02:54 android13-5.10-lts f5a34916f66d 0909d65f .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-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/05/20 02:24 android13-5.10-lts f5a34916f66d 0909d65f .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-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/02/24 04:54 android13-5.10-lts e8b14e1cefe8 41d2fa6a .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/02/24 04:18 android13-5.10-lts e8b14e1cefe8 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/02/24 04:18 android13-5.10-lts e8b14e1cefe8 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
2026/02/24 04:17 android13-5.10-lts e8b14e1cefe8 41d2fa6a .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-10 KASAN: use-after-free Read in ext4_xattr_ibody_get
* Struck through repros no longer work on HEAD.