syzbot


KASAN: slab-out-of-bounds Read in ext4_get_inode_usage

Status: upstream: reported C repro on 2026/05/16 23:51
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+45e23e06cf4d881e85a5@syzkaller.appspotmail.com
First crash: 3d11h, last: 3d10h
Bug presence (2)
Date Name Commit Repro Result
2026/05/17 lts (merge base) de8dfb3f0278 C [report] lost connection to test machine
2026/05/17 upstream (ToT) 6916d5703ddf C [report] lost connection to test machine
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in ext4_get_inode_usage 19 C 42 2d02h 4d15h 0/2 upstream: reported C repro on 2026/05/15 18:41
linux-5.15 KASAN: use-after-free Read in ext4_get_inode_usage 19 C 2 3d03h 3d08h 0/3 upstream: reported C repro on 2026/05/17 01:53

Sample crash report:
EXT4-fs (loop2): Warning: mounting with an experimental mount option 'dioread_nolock' for blocksize < PAGE_SIZE
[EXT4 FS bs=1024, gc=1, bpg=131072, ipg=32, mo=e855c01c, mo2=0003]
System zones: 0-1, 3-36
EXT4-fs (loop2): mounted filesystem without journal. Opts: grpquota,delalloc,resuid=0x0000000000000000,debug,dioread_nolock,bsddf,nomblk_io_submit,noauto_da_alloc,,errors=continue. Quota mode: writeback.
==================================================================
BUG: KASAN: use-after-free in ext4_get_inode_usage+0x3a1/0x520 fs/ext4/xattr.c:821
Read of size 4 at addr ffff888124dbb070 by task syz.2.17/374

CPU: 1 PID: 374 Comm: syz.2.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+0xf1/0x140 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_get_inode_usage+0x3a1/0x520 fs/ext4/xattr.c:821
 __dquot_transfer+0x192/0x2150 fs/quota/dquot.c:2015
 dquot_transfer+0x2f1/0x460 fs/quota/dquot.c:2167
 ext4_setattr+0x700/0x1ac0 fs/ext4/inode.c:5508
 notify_change+0xbca/0xe90 fs/attr.c:505
 chown_common+0x4b8/0x680 fs/open.c:681
 vfs_fchown fs/open.c:749 [inline]
 ksys_fchown+0xef/0x160 fs/open.c:760
 __do_sys_fchown fs/open.c:768 [inline]
 __se_sys_fchown fs/open.c:766 [inline]
 __x64_sys_fchown+0x7a/0x90 fs/open.c:766
 x64_sys_call+0x95f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:94
 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: 0033:0x7fef4971fe59
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:00007fef49582028 EFLAGS: 00000246 ORIG_RAX: 000000000000005d
RAX: ffffffffffffffda RBX: 00007fef49998fa0 RCX: 00007fef4971fe59
RDX: 000000000000ee01 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fef497b5d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fef49999038 R14: 00007fef49998fa0 R15: 00007ffeae0673d8
 </TASK>

Allocated by task 245:
 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+0xbd/0xf0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x4f/0x2b0 mm/slab.h:550
 kmem_cache_alloc_bulk+0x27b/0x340 mm/slub.c:3743
 napi_skb_cache_get net/core/skbuff.c:179 [inline]
 __alloc_skb+0x526/0x740 net/core/skbuff.c:414
 __napi_alloc_skb+0x162/0x2e0 net/core/skbuff.c:569
 napi_alloc_skb include/linux/skbuff.h:3102 [inline]
 page_to_skb+0x287/0xb60 drivers/net/virtio_net.c:474
 receive_mergeable drivers/net/virtio_net.c:1102 [inline]
 receive_buf+0xcc7/0x4c50 drivers/net/virtio_net.c:1212
 virtnet_receive drivers/net/virtio_net.c:1504 [inline]
 virtnet_poll+0x570/0xf40 drivers/net/virtio_net.c:1617
 __napi_poll+0xbe/0x590 net/core/dev.c:7109
 napi_poll net/core/dev.c:7176 [inline]
 net_rx_action+0x389/0x900 net/core/dev.c:7266
 handle_softirqs+0x250/0x560 kernel/softirq.c:583
 __do_softirq kernel/softirq.c:621 [inline]
 invoke_softirq kernel/softirq.c:443 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
 irq_exit_rcu+0x9/0x10 kernel/softirq.c:682
 common_interrupt+0xbe/0xe0 arch/x86/kernel/irq.c:242
 asm_common_interrupt+0x27/0x40 arch/x86/include/asm/idtentry.h:667

Freed by task 244:
 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:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kmem_cache_free+0x100/0x320 mm/slub.c:3544
 kfree_skbmem+0x10c/0x180 net/core/skbuff.c:-1
 __kfree_skb+0x58/0x70 net/core/skbuff.c:758
 sk_eat_skb include/net/sock.h:2799 [inline]
 tcp_recvmsg_locked+0x14cd/0x26f0 net/ipv4/tcp.c:2520
 tcp_recvmsg+0x23c/0x770 net/ipv4/tcp.c:2566
 inet_recvmsg+0x13a/0x480 net/ipv4/af_inet.c:861
 sock_recvmsg_nosec net/socket.c:966 [inline]
 sock_recvmsg net/socket.c:984 [inline]
 sock_read_iter+0x2b8/0x380 net/socket.c:1057
 call_read_iter include/linux/fs.h:2206 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x6c9/0xc40 fs/read_write.c:485
 ksys_read+0x149/0x250 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 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 ffff888124dbb000
 which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 112 bytes inside of
 248-byte region [ffff888124dbb000, ffff888124dbb0f8)
The buggy address belongs to the page:
page:ffffea0004936ec0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x124dbb
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff8881081aa780
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 0x12a20(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY), pid 245, ts 17669815962, free_ts 17669742792
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x2d3a/0x2dc0 mm/page_alloc.c:4485
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5822
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa1/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x381/0x810 mm/slub.c:3033
 kmem_cache_alloc_bulk+0xf7/0x340 mm/slub.c:3719
 napi_skb_cache_get net/core/skbuff.c:179 [inline]
 __alloc_skb+0x526/0x740 net/core/skbuff.c:414
 __napi_alloc_skb+0x162/0x2e0 net/core/skbuff.c:569
 napi_alloc_skb include/linux/skbuff.h:3102 [inline]
 page_to_skb+0x287/0xb60 drivers/net/virtio_net.c:474
 receive_mergeable drivers/net/virtio_net.c:1102 [inline]
 receive_buf+0xcc7/0x4c50 drivers/net/virtio_net.c:1212
 virtnet_receive drivers/net/virtio_net.c:1504 [inline]
 virtnet_poll+0x570/0xf40 drivers/net/virtio_net.c:1617
 __napi_poll+0xbe/0x590 net/core/dev.c:7109
 napi_poll net/core/dev.c:7176 [inline]
 net_rx_action+0x389/0x900 net/core/dev.c:7266
 handle_softirqs+0x250/0x560 kernel/softirq.c:583
 __do_softirq kernel/softirq.c:621 [inline]
 invoke_softirq kernel/softirq.c:443 [inline]
 __irq_exit_rcu+0x52/0xf0 kernel/softirq.c:670
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x542/0x550 mm/page_alloc.c:3534
 free_unref_page+0xae/0x540 mm/page_alloc.c:3616
 __put_single_page mm/swap.c:98 [inline]
 __put_page+0xad/0xe0 mm/swap.c:129
 put_page include/linux/mm.h:1306 [inline]
 anon_pipe_buf_release+0x183/0x200 fs/pipe.c:137
 pipe_buf_release include/linux/pipe_fs_i.h:219 [inline]
 pipe_read+0x53b/0x1010 fs/pipe.c:323
 call_read_iter include/linux/fs.h:2206 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x6c9/0xc40 fs/read_write.c:485
 ksys_read+0x149/0x250 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 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

Memory state around the buggy address:
 ffff888124dbaf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888124dbaf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888124dbb000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                             ^
 ffff888124dbb080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
 ffff888124dbb100: fc fc fc fc fc fc fc fc fa 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
2026/05/17 00:03 android13-5.15-lts 7f4b368e0410 de5aae85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_get_inode_usage
2026/05/16 23:43 android13-5.15-lts 7f4b368e0410 de5aae85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_get_inode_usage
2026/05/16 22:29 android13-5.15-lts 7f4b368e0410 de5aae85 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_get_inode_usage
* Struck through repros no longer work on HEAD.