syzbot


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: 14d, last: 2h08m
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/03/10 05:57 10m retest repro android13-5.10-lts report log

Sample crash report:
EXT4-fs (loop2): Ignoring removed orlov option
EXT4-fs (loop2): mounted filesystem without journal. Opts: block_validity,bsddf,nombcache,inode_readahead_blks=0x0000000000000000,debug_want_extra_isize=0x0000000000000080,orlov,nogrpid,noauto_da_alloc,grpjquota=,,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 ffff88811147a004 by task syz.2.20/386

CPU: 0 PID: 386 Comm: syz.2.20 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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+0x9fa/0x1760 fs/ext4/inode.c:5722
 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_fchmodat fs/open.c:635 [inline]
 __se_sys_fchmodat fs/open.c:632 [inline]
 __x64_sys_fchmodat+0x7b/0x90 fs/open.c:632
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f2233b85629
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:00007fff13c70298 EFLAGS: 00000246 ORIG_RAX: 000000000000010c
RAX: ffffffffffffffda RBX: 00007f2233dfefa0 RCX: 00007f2233b85629
RDX: 000000000000017f RSI: 0000200000000300 RDI: ffffffffffffff9c
RBP: 00007f2233c1bb39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2233dfefac R14: 00007f2233dfefa0 R15: 00007f2233dfefa0

Allocated by task 288:
 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
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x11e/0x460 mm/mempool.c:393
 bio_alloc_bioset+0x18c/0x570 block/bio.c:486
 bio_alloc include/linux/bio.h:412 [inline]
 mpage_alloc fs/mpage.c:115 [inline]
 do_mpage_readpage+0x1441/0x1a40 fs/mpage.c:342
 mpage_readahead+0x272/0x560 fs/mpage.c:425
 blkdev_readahead+0x1c/0x20 fs/block_dev.c:653
 read_pages+0x17b/0xb60 mm/readahead.c:140
 page_cache_ra_unbounded+0x693/0x7e0 mm/readahead.c:248
 do_page_cache_ra mm/readahead.c:277 [inline]
 force_page_cache_ra+0x3a9/0x400 mm/readahead.c:308
 page_cache_sync_ra+0x237/0x2a0 mm/readahead.c:582
 page_cache_sync_readahead include/linux/pagemap.h:837 [inline]
 generic_file_buffered_read+0x574/0x2770 mm/filemap.c:2250
 generic_file_read_iter+0x11e/0x5c0 mm/filemap.c:2568
 blkdev_read_iter+0x12f/0x160 fs/block_dev.c:1956
 call_read_iter include/linux/fs.h:2060 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x62a/0xa60 fs/read_write.c:496
 ksys_read+0x149/0x250 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 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
 mempool_free_slab+0x1d/0x30 mm/mempool.c:520
 mempool_free+0xd8/0x340 mm/mempool.c:502
 bio_free+0x24a/0x360 block/bio.c:266
 bio_put+0xbf/0x110 block/bio.c:-1
 mpage_end_io+0x2ea/0x560 fs/mpage.c:76
 bio_endio+0x646/0x860 block/bio.c:1458
 req_bio_endio block/blk-core.c:263 [inline]
 blk_update_request+0x74a/0x1090 block/blk-core.c:1468
 blk_mq_end_request+0x41/0x80 block/blk-mq.c:572
 lo_complete_rq+0x147/0x2d0 drivers/block/loop.c:490
 blk_done_softirq+0x26f/0x2f0 block/blk-mq.c:596
 __do_softirq+0x255/0x563 kernel/softirq.c:309

The buggy address belongs to the object at ffff88811147a000
 which belongs to the cache bio-0 of size 216
The buggy address is located 4 bytes inside of
 216-byte region [ffff88811147a000, ffff88811147a0d8)
The buggy address belongs to the page:
page:ffffea0004451e80 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11147a
flags: 0x4000000000000200(slab)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff888107fbe780
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 0x192880(GFP_NOWAIT|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 288, ts 31234995485, free_ts 31174684175
 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:5370
 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
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x11e/0x460 mm/mempool.c:393
 bio_alloc_bioset+0x18c/0x570 block/bio.c:486
 bio_alloc include/linux/bio.h:412 [inline]
 mpage_alloc fs/mpage.c:115 [inline]
 do_mpage_readpage+0x1441/0x1a40 fs/mpage.c:342
 mpage_readahead+0x272/0x560 fs/mpage.c:425
 blkdev_readahead+0x1c/0x20 fs/block_dev.c:653
 read_pages+0x17b/0xb60 mm/readahead.c:140
 page_cache_ra_unbounded+0x693/0x7e0 mm/readahead.c:248
 do_page_cache_ra mm/readahead.c:277 [inline]
 force_page_cache_ra+0x3a9/0x400 mm/readahead.c:308
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_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5431 [inline]
 __free_pages+0xd8/0x3b0 mm/page_alloc.c:5440
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab mm/slub.c:1920 [inline]
 unfreeze_partials+0x15f/0x190 mm/slub.c:2415
 put_cpu_partial+0xc1/0x180 mm/slub.c:2451
 __slab_free+0x2c9/0x3a0 mm/slub.c:3100
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
 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
 getname_flags+0xb9/0x500 fs/namei.c:141
 getname fs/namei.c:212 [inline]
 __do_sys_unlink fs/namei.c:4090 [inline]
 __se_sys_unlink fs/namei.c:4088 [inline]
 __x64_sys_unlink+0x3c/0x50 fs/namei.c:4088
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46

Memory state around the buggy address:
 ffff888111479f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888111479f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88811147a000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88811147a080: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
 ffff88811147a100: 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

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.