[Android 5.15] KASAN: slab-out-of-bounds Read in ext4_get_inode_usage

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7f4b368e0410 Merge 5.15.206 into android13-5.15-lts
git tree: android13-5.15-lts
console output: https://syzkaller.appspot.com/x/log.txt?x=14153f6c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=daefb08bb2811735
dashboard link: https://syzkaller.appspot.com/bug?extid=45e23e06cf4d881e85a5
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=158b58ec580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16cda0ec580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4451345c6abf/disk-7f4b368e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5e418dd662b5/vmlinux-7f4b368e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a0939c5bbfe1/bzImage-7f4b368e.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/9a5f85d47732/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=118b58ec580000)
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/7362561e7817/mount_6.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12cda0ec580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+45e23e...@syzkaller.appspotmail.com

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 ffff88810fa67070 by task syz.2.23/386

CPU: 0 PID: 386 Comm: syz.2.23 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: 0033:0x7f4c9a37be59
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:00007ffe2ba9d648 EFLAGS: 00000246 ORIG_RAX: 000000000000005d
RAX: ffffffffffffffda RBX: 00007f4c9a5f4fa0 RCX: 00007f4c9a37be59
RDX: 000000000000ee01 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007f4c9a411d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4c9a5f4fac R14: 00007f4c9a5f4fa0 R15: 00007f4c9a5f4fa0
</TASK>

Allocated by task 349:
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
slab_alloc_node mm/slub.c:3245 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc+0xf7/0x260 mm/slub.c:3260
kmem_cache_alloc_node include/linux/slab.h:492 [inline]
__alloc_skb+0xe0/0x740 net/core/skbuff.c:416
alloc_skb include/linux/skbuff.h:1183 [inline]
nlmsg_new include/net/netlink.h:953 [inline]
rtmsg_ifa+0xfa/0x1d0 net/ipv4/devinet.c:1927
__inet_insert_ifa+0x878/0xa90 net/ipv4/devinet.c:567
inet_rtm_newaddr+0x8d3/0x15e0 net/ipv4/devinet.c:967
rtnetlink_rcv_msg+0xa4b/0xce0 net/core/rtnetlink.c:5653
netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2511
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5671
netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1348
netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1922
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x46d/0x620 net/socket.c:2062
__do_sys_sendto net/socket.c:2074 [inline]
__se_sys_sendto net/socket.c:2070 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2070
x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
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

Freed by task 349:
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 net/core/skbuff.c:758 [inline]
consume_skb+0xb3/0x1f0 net/core/skbuff.c:930
netlink_broadcast_filtered+0x113a/0x1230 net/netlink/af_netlink.c:1538
netlink_broadcast net/netlink/af_netlink.c:1560 [inline]
nlmsg_multicast include/net/netlink.h:1033 [inline]
nlmsg_notify+0xed/0x1b0 net/netlink/af_netlink.c:2554
rtnl_notify+0x9a/0xc0 net/core/rtnetlink.c:762
rtmsg_ifa+0x143/0x1d0 net/ipv4/devinet.c:1938
__inet_insert_ifa+0x878/0xa90 net/ipv4/devinet.c:567
inet_rtm_newaddr+0x8d3/0x15e0 net/ipv4/devinet.c:967
rtnetlink_rcv_msg+0xa4b/0xce0 net/core/rtnetlink.c:5653
netlink_rcv_skb+0x1f5/0x440 net/netlink/af_netlink.c:2511
rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5671
netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
netlink_unicast+0x876/0xa40 net/netlink/af_netlink.c:1348
netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1922
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
__sys_sendto+0x46d/0x620 net/socket.c:2062
__do_sys_sendto net/socket.c:2074 [inline]
__se_sys_sendto net/socket.c:2070 [inline]
__x64_sys_sendto+0xe5/0x100 net/socket.c:2070
x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
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 ffff88810fa67000
which belongs to the cache skbuff_head_cache of size 248
The buggy address is located 112 bytes inside of
248-byte region [ffff88810fa67000, ffff88810fa670f8)
The buggy address belongs to the page:
page:ffffea00043e99c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10fa67
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff8881081ab380
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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 106, ts 5577458146, free_ts 5577064654
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
__slab_alloc+0x49/0x90 mm/slub.c:3120
slab_alloc_node mm/slub.c:3211 [inline]
slab_alloc mm/slub.c:3255 [inline]
kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
kmem_cache_alloc_node include/linux/slab.h:492 [inline]
__alloc_skb+0xe0/0x740 net/core/skbuff.c:416
alloc_skb include/linux/skbuff.h:1183 [inline]
alloc_skb_with_frags+0xa8/0x620 net/core/skbuff.c:6194
sock_alloc_send_pskb+0x87f/0x9a0 net/core/sock.c:2542
unix_dgram_sendmsg+0x5f7/0x1890 net/unix/af_unix.c:1816
sock_sendmsg_nosec net/socket.c:704 [inline]
__sock_sendmsg net/socket.c:716 [inline]
sock_write_iter+0x2a6/0x3a0 net/socket.c:1079
call_write_iter include/linux/fs.h:2212 [inline]
new_sync_write fs/read_write.c:507 [inline]
vfs_write+0x835/0xfd0 fs/read_write.c:594
ksys_write+0x149/0x250 fs/read_write.c:647
__do_sys_write fs/read_write.c:659 [inline]
__se_sys_write fs/read_write.c:656 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:656
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
free_the_page mm/page_alloc.c:805 [inline]
__free_pages+0x6c/0x100 mm/page_alloc.c:5898
free_pages+0x82/0x90 mm/page_alloc.c:5909
selinux_genfs_get_sid+0x20b/0x250 security/selinux/hooks.c:1381
inode_doinit_with_dentry+0x87a/0xd80 security/selinux/hooks.c:1576
selinux_d_instantiate+0x27/0x40 security/selinux/hooks.c:6495
security_d_instantiate+0x9e/0xf0 security/security.c:2075
d_splice_alias+0x6d/0x390 fs/dcache.c:3073
kernfs_iop_lookup+0x2c2/0x310 fs/kernfs/dir.c:1175
lookup_open fs/namei.c:3448 [inline]
open_last_lookups fs/namei.c:3540 [inline]
path_openat+0xfc9/0x2f20 fs/namei.c:3747
do_filp_open+0x1e2/0x410 fs/namei.c:3777
do_sys_openat2+0x15e/0x7f0 fs/open.c:1236
do_sys_open fs/open.c:1252 [inline]
__do_sys_openat fs/open.c:1268 [inline]
__se_sys_openat fs/open.c:1263 [inline]
__x64_sys_openat+0x136/0x160 fs/open.c:1263
x64_sys_call+0x219/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80

Memory state around the buggy address:
ffff88810fa66f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff88810fa66f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88810fa67000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88810fa67080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
ffff88810fa67100: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
==================================================================


---
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