[v6.1] KASAN: use-after-free Read in pressure_write

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 58485ff1a74f Linux 6.1.141
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=16e59282580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c186557a18643a0b
dashboard link: https://syzkaller.appspot.com/bug?extid=b2a476e56082a38911bd
compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/467cd5b7e60b/disk-58485ff1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/df87a7313b47/vmlinux-58485ff1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/597ae3da22ce/bzImage-58485ff1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b2a476...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in pressure_write+0x1e3/0x4a0 kernel/cgroup/cgroup.c:3778
Read of size 8 at addr ffff8881437fe608 by task syz.4.480/6641

CPU: 1 PID: 6641 Comm: syz.4.480 Not tainted 6.1.141-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
print_address_description mm/kasan/report.c:316 [inline]
print_report+0xa8/0x220 mm/kasan/report.c:427
kasan_report+0x10b/0x140 mm/kasan/report.c:531
pressure_write+0x1e3/0x4a0 kernel/cgroup/cgroup.c:3778
cgroup_file_write+0x2f8/0x660 kernel/cgroup/cgroup.c:4077
kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2265 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x44c/0x960 fs/read_write.c:584
ksys_write+0x143/0x240 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f0ec258e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0ec33a4038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f0ec27b6160 RCX: 00007f0ec258e929
RDX: 000000000000002f RSI: 00002000000001c0 RDI: 0000000000000006
RBP: 00007f0ec2610ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f0ec27b6160 R15: 00007ffe43752658
</TASK>

Allocated by task 6641:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
____kasan_kmalloc mm/kasan/common.c:374 [inline]
__kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:383
kmalloc include/linux/slab.h:563 [inline]
kzalloc include/linux/slab.h:699 [inline]
cgroup_file_open+0x85/0x2a0 kernel/cgroup/cgroup.c:4023
kernfs_fop_open+0xa01/0xcc0 fs/kernfs/file.c:748
do_dentry_open+0x7e9/0x10d0 fs/open.c:882
do_open fs/namei.c:3626 [inline]
path_openat+0x25c6/0x2e70 fs/namei.c:3783
do_filp_open+0x1c1/0x3c0 fs/namei.c:3810
do_sys_openat2+0x142/0x490 fs/open.c:1318
do_sys_open fs/open.c:1334 [inline]
__do_sys_openat fs/open.c:1350 [inline]
__se_sys_openat fs/open.c:1345 [inline]
__x64_sys_openat+0x135/0x160 fs/open.c:1345
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 6657:
kasan_save_stack mm/kasan/common.c:45 [inline]
kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
kasan_slab_free include/linux/kasan.h:177 [inline]
slab_free_hook mm/slub.c:1724 [inline]
slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1750
slab_free mm/slub.c:3661 [inline]
__kmem_cache_free+0xb6/0x1f0 mm/slub.c:3674
kernfs_release_file+0x128/0x2c0 fs/kernfs/file.c:788
kernfs_drain_open_files+0x2b4/0x4a0 fs/kernfs/file.c:857
kernfs_drain+0x4b4/0x660 fs/kernfs/dir.c:513
__kernfs_remove+0x3f6/0x6d0 fs/kernfs/dir.c:1461
kernfs_remove_by_name_ns+0xd8/0x150 fs/kernfs/dir.c:1666
kernfs_remove_by_name include/linux/kernfs.h:622 [inline]
cgroup_rm_file kernel/cgroup/cgroup.c:1703 [inline]
cgroup_addrm_files+0x5c6/0xb80 kernel/cgroup/cgroup.c:4270
cgroup_destroy_locked+0x4d2/0x7f0 kernel/cgroup/cgroup.c:5928
cgroup_rmdir+0x3c/0x3e0 kernel/cgroup/cgroup.c:5967
kernfs_iop_rmdir+0x23b/0x3b0 fs/kernfs/dir.c:1239
vfs_rmdir+0x36c/0x4d0 fs/namei.c:4191
do_rmdir+0x288/0x5e0 fs/namei.c:4252
__do_sys_rmdir fs/namei.c:4271 [inline]
__se_sys_rmdir fs/namei.c:4269 [inline]
__x64_sys_rmdir+0x45/0x50 fs/namei.c:4269
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
kasan_save_stack+0x3a/0x60 mm/kasan/common.c:45
__kasan_record_aux_stack+0xb2/0xc0 mm/kasan/generic.c:486
call_rcu+0x14b/0x970 kernel/rcu/tree.c:2845
tnode_free net/ipv4/fib_trie.c:496 [inline]
replace+0x237/0x5c0 net/ipv4/fib_trie.c:522
inflate net/ipv4/fib_trie.c:624 [inline]
resize+0x1019/0x26e0 net/ipv4/fib_trie.c:869
trie_rebalance net/ipv4/fib_trie.c:1106 [inline]
fib_insert_node net/ipv4/fib_trie.c:1150 [inline]
fib_insert_alias+0xabe/0x1210 net/ipv4/fib_trie.c:1164
fib_table_insert+0x679/0x1b50 net/ipv4/fib_trie.c:1359
fib_magic+0x2c1/0x390 net/ipv4/fib_frontend.c:1118
fib_add_ifaddr+0x140/0x5e0 net/ipv4/fib_frontend.c:1140
fib_inetaddr_event+0x13c/0x1c0 net/ipv4/fib_frontend.c:1454
notifier_call_chain kernel/notifier.c:87 [inline]
blocking_notifier_call_chain+0x103/0x1b0 kernel/notifier.c:382
__inet_insert_ifa+0x9aa/0xb60 net/ipv4/devinet.c:569
inet_rtm_newaddr+0x930/0x1890 net/ipv4/devinet.c:971
rtnetlink_rcv_msg+0x79b/0xed0 net/core/rtnetlink.c:6153
netlink_rcv_skb+0x1de/0x420 net/netlink/af_netlink.c:2493
netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
netlink_unicast+0x74c/0x8c0 net/netlink/af_netlink.c:1337
netlink_sendmsg+0x89e/0xbc0 net/netlink/af_netlink.c:1859
sock_sendmsg_nosec net/socket.c:718 [inline]
__sock_sendmsg net/socket.c:730 [inline]
__sys_sendto+0x44f/0x5c0 net/socket.c:2153
__do_sys_sendto net/socket.c:2165 [inline]
__se_sys_sendto net/socket.c:2161 [inline]
__x64_sys_sendto+0xda/0xf0 net/socket.c:2161
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff8881437fe600
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 8 bytes inside of
192-byte region [ffff8881437fe600, ffff8881437fe6c0)

The buggy address belongs to the physical page:
page:ffffea00050dff80 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8881437fef00 pfn:0x1437fe
flags: 0x57ff00000000200(slab|node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000200 ffffea0005169940 dead000000000002 ffff888017441a00
raw: ffff8881437fef00 0000000080100003 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 1, tgid 1 (swapper/0), ts 9098407805, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2532
prep_new_page mm/page_alloc.c:2539 [inline]
get_page_from_freelist+0x1a26/0x1ac0 mm/page_alloc.c:4328
__alloc_pages+0x1df/0x4e0 mm/page_alloc.c:5614
alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2115
alloc_slab_page+0x5d/0x160 mm/slub.c:1794
allocate_slab mm/slub.c:1939 [inline]
new_slab+0x87/0x2c0 mm/slub.c:1992
___slab_alloc+0xbc6/0x1220 mm/slub.c:3180
__slab_alloc mm/slub.c:3279 [inline]
slab_alloc_node mm/slub.c:3364 [inline]
__kmem_cache_alloc_node+0x1a0/0x260 mm/slub.c:3437
kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
kmalloc include/linux/slab.h:563 [inline]
kzalloc include/linux/slab.h:699 [inline]
call_usermodehelper_setup+0x8a/0x260 kernel/umh.c:366
kobject_uevent_env+0x659/0x8a0 lib/kobject_uevent.c:629
disk_uevent+0x278/0x450 block/genhd.c:352
device_add_disk+0xd23/0x1020 block/genhd.c:537
add_disk include/linux/blkdev.h:757 [inline]
loop_add+0x6f2/0x9b0 drivers/block/loop.c:2071
loop_init+0x173/0x226 drivers/block/loop.c:2263
do_one_initcall+0x214/0x7a0 init/main.c:1298
page_owner free stack trace missing

Memory state around the buggy address:
ffff8881437fe500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881437fe580: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8881437fe600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8881437fe680: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8881437fe700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.