syzbot


KASAN: slab-use-after-free Read in __ext4_iget

Status: upstream: reported on 2025/08/15 02:29
Reported-by: syzbot+a08013e80f8d0b18d42b@syzkaller.appspotmail.com
First crash: 258d, last: 3d11h
Similar bugs (11)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in __ext4_iget fs reiserfs 19 278 821d 1058d 0/29 auto-obsoleted due to no activity on 2024/04/09 13:42
linux-6.1 KASAN: use-after-free Read in __ext4_iget 19 2 595d 637d 0/3 auto-obsoleted due to no activity on 2024/12/21 07:26
android-54 KASAN: use-after-free Read in __ext4_iget (3) 19 C 58 339d 413d 0/2 upstream: reported C repro on 2025/03/13 17:21
linux-5.15 KASAN: use-after-free Read in __ext4_iget 19 47 23h35m 820d 0/3 upstream: reported on 2024/01/31 03:06
linux-6.1 KASAN: slab-out-of-bounds Read in __ext4_iget (2) 19 35 8d10h 452d 0/3 upstream: reported on 2025/02/01 20:39
android-5-15 KASAN: use-after-free Read in __ext4_iget origin:lts 19 C 660 7d12h 394d 0/2 upstream: reported C repro on 2025/04/01 19:00
linux-5.15 KASAN: slab-out-of-bounds Read in __ext4_iget 19 6 925d 969d 0/3 auto-obsoleted due to no activity on 2024/01/25 22:09
android-54 KASAN: use-after-free Read in __ext4_iget 19 13 798d 1005d 0/2 auto-obsoleted due to no activity on 2024/05/22 19:07
android-5-10 KASAN: use-after-free Read in __ext4_iget 19 C 502 1d17h 418d 0/2 upstream: reported C repro on 2025/03/08 14:28
android-54 KASAN: use-after-free Read in __ext4_iget (2) 19 4 680d 698d 0/2 auto-obsoleted due to no activity on 2024/09/17 10:19
linux-6.1 KASAN: slab-out-of-bounds Read in __ext4_iget 19 14 760d 1015d 0/3 auto-obsoleted due to no activity on 2024/07/09 19:10

Sample crash report:
loop1: detected capacity change from 0 to 512
EXT4-fs: Ignoring removed i_version option
==================================================================
BUG: KASAN: slab-use-after-free in check_igot_inode fs/ext4/inode.c:-1 [inline]
BUG: KASAN: slab-use-after-free in __ext4_iget+0x2c0/0x3f40 fs/ext4/inode.c:4850
Read of size 8 at addr ffff88805b420c70 by task syz.1.16718/13692

CPU: 0 PID: 13692 Comm: syz.1.16718 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 check_igot_inode fs/ext4/inode.c:-1 [inline]
 __ext4_iget+0x2c0/0x3f40 fs/ext4/inode.c:4850
 __ext4_fill_super fs/ext4/super.c:5517 [inline]
 ext4_fill_super+0x503a/0x67b0 fs/ext4/super.c:5744
 get_tree_bdev+0x3f3/0x520 fs/super.c:1591
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3386
 do_mount fs/namespace.c:3726 [inline]
 __do_sys_mount fs/namespace.c:3935 [inline]
 __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe6e1b9e04a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fe6e2b38e58 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe6e2b38ee0 RCX: 00007fe6e1b9e04a
RDX: 0000200000000000 RSI: 0000200000000040 RDI: 00007fe6e2b38ea0
RBP: 0000200000000000 R08: 00007fe6e2b38ee0 R09: 0000000000000014
R10: 0000000000000014 R11: 0000000000000246 R12: 0000200000000040
R13: 00007fe6e2b38ea0 R14: 00000000000003f7 R15: 00002000000004c0
 </TASK>

Allocated by task 7166:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc_lru+0x111/0x2d0 mm/slub.c:3526
 alloc_inode_sb include/linux/fs.h:2946 [inline]
 reiserfs_alloc_inode+0x2a/0xc0 fs/reiserfs/super.c:642
 alloc_inode fs/inode.c:261 [inline]
 iget5_locked+0xa2/0x260 fs/inode.c:1314
 reiserfs_fill_super+0x11d7/0x23b0 fs/reiserfs/super.c:2053
 mount_bdev+0x221/0x2d0 fs/super.c:1643
 legacy_get_tree+0xea/0x180 fs/fs_context.c:662
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3386
 do_mount fs/namespace.c:3726 [inline]
 __do_sys_mount fs/namespace.c:3935 [inline]
 __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:46
 __kasan_record_aux_stack+0xaf/0xc0 mm/kasan/generic.c:492
 __call_rcu_common kernel/rcu/tree.c:2721 [inline]
 call_rcu+0x153/0x950 kernel/rcu/tree.c:2837
 destroy_inode fs/inode.c:316 [inline]
 evict+0x835/0x8d0 fs/inode.c:720
 reiserfs_fill_super+0x1479/0x23b0 fs/reiserfs/super.c:2078
 mount_bdev+0x221/0x2d0 fs/super.c:1643
 legacy_get_tree+0xea/0x180 fs/fs_context.c:662
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3386
 do_mount fs/namespace.c:3726 [inline]
 __do_sys_mount fs/namespace.c:3935 [inline]
 __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff88805b4206a0
 which belongs to the cache reiser_inode_cache of size 1568
The buggy address is located 1488 bytes inside of
 freed 1568-byte region [ffff88805b4206a0, ffff88805b420cc0)

The buggy address belongs to the physical page:
page:ffffea00016d0800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88805b424240 pfn:0x5b420
head:ffffea00016d0800 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888025f35301
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff88801f2f2c80 dead000000000122 0000000000000000
raw: ffff88805b424240 000000008013000a 00000001ffffffff ffff888025f35301
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0x1d20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL|__GFP_RECLAIMABLE), pid 6091, tgid 6090 (syz.3.116), ts 84897541179, free_ts 16693606409
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
 prep_new_page mm/page_alloc.c:1588 [inline]
 get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
 alloc_slab_page+0x5d/0x160 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5d/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc_lru+0x1aa/0x2d0 mm/slub.c:3526
 alloc_inode_sb include/linux/fs.h:2946 [inline]
 reiserfs_alloc_inode+0x2a/0xc0 fs/reiserfs/super.c:642
 alloc_inode fs/inode.c:261 [inline]
 iget5_locked+0xa2/0x260 fs/inode.c:1314
 reiserfs_fill_super+0x11d7/0x23b0 fs/reiserfs/super.c:2053
 mount_bdev+0x221/0x2d0 fs/super.c:1643
 legacy_get_tree+0xea/0x180 fs/fs_context.c:662
 vfs_get_tree+0x8c/0x280 fs/super.c:1764
 do_new_mount+0x24b/0xa40 fs/namespace.c:3386
 do_mount fs/namespace.c:3726 [inline]
 __do_sys_mount fs/namespace.c:3935 [inline]
 __se_sys_mount+0x2e7/0x3d0 fs/namespace.c:3912
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1181 [inline]
 free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
 free_contig_range+0xa1/0x150 mm/page_alloc.c:6420
 destroy_args+0x80/0x850 mm/debug_vm_pgtable.c:1015
 debug_vm_pgtable+0x411/0x440 mm/debug_vm_pgtable.c:1400
 do_one_initcall+0x242/0x790 init/main.c:1250
 do_initcall_level+0x137/0x1f0 init/main.c:1312
 do_initcalls+0x69/0xd0 init/main.c:1328
 kernel_init_freeable+0x3ed/0x580 init/main.c:1565
 kernel_init+0x1d/0x1c0 init/main.c:1455
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Memory state around the buggy address:
 ffff88805b420b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88805b420b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88805b420c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff88805b420c80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
 ffff88805b420d00: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================

Crashes (17):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/27 09:01 linux-6.6.y 9760bf04666d 0f700595 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/04/25 00:23 linux-6.6.y 9760bf04666d 9c2d0995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/04/13 22:40 linux-6.6.y 8cee53b8eaeb 1a086e7c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/03/07 00:30 linux-6.6.y 4fc00fe35d46 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/01/26 10:17 linux-6.6.y cbb31f77b879 a4c52dd6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/01/23 09:45 linux-6.6.y cbb31f77b879 e2b1b6e6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/01/17 16:33 linux-6.6.y cbb31f77b879 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2025/10/20 14:05 linux-6.6.y f231f248323d d422939c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2025/10/07 22:19 linux-6.6.y e617101e5626 7e2882b3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2025/08/21 13:39 linux-6.6.y bb9c90ab9c5a 3e79b825 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2025/08/19 13:22 linux-6.6.y bb9c90ab9c5a 254a27c1 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2025/08/15 02:28 linux-6.6.y 3a8ababb8b6a 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in __ext4_iget
2026/04/02 10:03 linux-6.6.y c09fbcd31ae6 91bc79b0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: use-after-free Read in __ext4_iget
2026/03/21 03:52 linux-6.6.y 4fc00fe35d46 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __ext4_iget
2026/02/13 05:09 linux-6.6.y 1b4ef5214f17 6a673c50 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __ext4_iget
2026/01/23 21:58 linux-6.6.y cbb31f77b879 4f25b9b4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __ext4_iget
2025/10/17 21:49 linux-6.6.y 0bbbd97a442d 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-out-of-bounds Read in __ext4_iget
* Struck through repros no longer work on HEAD.