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: 4d16h, last: 4d15h
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_listxattr origin:upstream 19 C 1 22d 22d 0/2 upstream: reported C repro on 2026/05/18 05:03

Sample crash report:
EXT4-fs (loop2): Mount option "noacl" will be removed by 3.5
Contact linux-ext4@vger.kernel.org if you think we should keep it.
EXT4-fs (loop2): Ignoring removed orlov option
EXT4-fs (loop2): mounted filesystem without journal. Opts: block_validity,bsddf,noacl,norecovery,debug_want_extra_isize=0x0000000000000080,orlov,nogrpid,noauto_da_alloc,norecovery,,errors=continue
==================================================================
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+0x4a6/0xc50 fs/ext4/xattr.c:765
Read of size 4 at addr ffff8881112f6090 by task syz.2.17/380

CPU: 1 PID: 380 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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
 ext4_xattr_list_entries fs/ext4/xattr.c:670 [inline]
 ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
 ext4_listxattr+0x4a6/0xc50 fs/ext4/xattr.c:765
 vfs_listxattr fs/xattr.c:420 [inline]
 listxattr+0x294/0x300 fs/xattr.c:715
 path_listxattr+0xe1/0x1b0 fs/xattr.c:739
 __do_sys_llistxattr fs/xattr.c:757 [inline]
 __se_sys_llistxattr fs/xattr.c:754 [inline]
 __x64_sys_llistxattr+0x7d/0x90 fs/xattr.c:754
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f18d815fe59
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:00007ffd5d95b1e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000c3
RAX: ffffffffffffffda RBX: 00007f18d83d8fa0 RCX: 00007f18d815fe59
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000400
RBP: 00007f18d81f5d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f18d83d8fac R14: 00007f18d83d8fa0 R15: 00007f18d83d8fa0

Allocated by task 94:
 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+0xbd/0xf0 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+0x162/0x2d0 mm/slub.c:2965
 kmem_cache_zalloc include/linux/slab.h:657 [inline]
 __alloc_file+0x28/0x320 fs/file_table.c:101
 alloc_empty_file+0x97/0x180 fs/file_table.c:151
 path_openat+0xf5/0x31c0 fs/namei.c:3503
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 12:
 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]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 file_free_rcu+0x93/0xa0 fs/file_table.c:50
 rcu_do_batch+0x4ef/0xab0 kernel/rcu/tree.c:2494
 rcu_core+0x577/0xd80 kernel/rcu/tree.c:2735
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
 __do_softirq+0x255/0x563 kernel/softirq.c:309

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x10b0 kernel/rcu/tree.c:3054
 file_free fs/file_table.c:58 [inline]
 __fput+0x5ad/0x770 fs/file_table.c:299
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop+0xcb/0xe0 kernel/entry/common.c:172
 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
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack+0xe/0x10 mm/kasan/generic.c:353
 task_work_add+0x27/0x1e0 kernel/task_work.c:38
 fput_many+0xe7/0x1a0 fs/file_table.c:342
 fput+0x1a/0x20 fs/file_table.c:358
 filp_close+0x105/0x150 fs/open.c:1335
 __close_fd+0x44/0x50 fs/file.c:716
 __do_sys_close fs/open.c:1348 [inline]
 __se_sys_close fs/open.c:1346 [inline]
 __x64_sys_close+0x66/0xb0 fs/open.c:1346
 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 ffff8881112f6000
 which belongs to the cache filp of size 296
The buggy address is located 144 bytes inside of
 296-byte region [ffff8881112f6000, ffff8881112f6128)
The buggy address belongs to the page:
page:ffffea000444bd80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1112f6
head:ffffea000444bd80 order:1 compound_mapcount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff88810018b200
raw: 0000000000000000 0000000000150015 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 105, ts 5205284405, 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+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]
 kmem_cache_alloc+0x1ac/0x2d0 mm/slub.c:2965
 kmem_cache_zalloc include/linux/slab.h:657 [inline]
 __alloc_file+0x28/0x320 fs/file_table.c:101
 alloc_empty_file+0x97/0x180 fs/file_table.c:151
 path_openat+0xf5/0x31c0 fs/namei.c:3503
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 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:
 ffff8881112f5f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881112f6000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881112f6080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8881112f6100: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
 ffff8881112f6180: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/04 21:41 android13-5.10-lts 4a079a5d30eb 197909be .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_listxattr
2026/06/04 20:58 android13-5.10-lts 4a079a5d30eb 197909be .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_listxattr
2026/06/04 20:12 android13-5.10-lts 4a079a5d30eb 197909be .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-10 KASAN: use-after-free Read in ext4_listxattr
* Struck through repros no longer work on HEAD.