[moderation] [v9fs?] KASAN: slab-use-after-free Write in v9fs_free_request

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 96fca68c4fbf Merge tag 'nfsd-6.9-3' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13567bb3180000
kernel config: https://syzkaller.appspot.com/x/.config?x=2dc5adfa93a8cfac
dashboard link: https://syzkaller.appspot.com/bug?extid=6e1f9eb45d7f7adac12e
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: i386
CC: [asma...@codewreck.org eri...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org linu...@crudebyte.com lu...@ionkov.net v9...@lists.linux.dev]

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

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-96fca68c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ff08b0ac058f/vmlinux-96fca68c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/499495148d50/bzImage-96fca68c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6e1f9e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
BUG: KASAN: slab-use-after-free in __refcount_sub_and_test include/linux/refcount.h:264 [inline]
BUG: KASAN: slab-use-after-free in __refcount_dec_and_test include/linux/refcount.h:307 [inline]
BUG: KASAN: slab-use-after-free in refcount_dec_and_test include/linux/refcount.h:325 [inline]
BUG: KASAN: slab-use-after-free in p9_fid_put include/net/9p/client.h:275 [inline]
BUG: KASAN: slab-use-after-free in v9fs_free_request+0x7d/0x110 fs/9p/vfs_addr.c:128
Write of size 4 at addr ffff888026991f8c by task kworker/u32:3/62

CPU: 2 PID: 62 Comm: kworker/u32:3 Not tainted 6.9.0-rc4-syzkaller-00031-g96fca68c4fbf #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: events_unbound v9fs_upload_to_server_worker
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:488
kasan_report+0xd9/0x110 mm/kasan/report.c:601
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
__refcount_sub_and_test include/linux/refcount.h:264 [inline]
__refcount_dec_and_test include/linux/refcount.h:307 [inline]
refcount_dec_and_test include/linux/refcount.h:325 [inline]
p9_fid_put include/net/9p/client.h:275 [inline]
v9fs_free_request+0x7d/0x110 fs/9p/vfs_addr.c:128
netfs_free_request+0x22f/0x6b0 fs/netfs/objects.c:97
netfs_put_request+0x19b/0x1f0 fs/netfs/objects.c:130
netfs_free_subrequest fs/netfs/objects.c:178 [inline]
netfs_put_subrequest+0x408/0x6c0 fs/netfs/objects.c:192
v9fs_upload_to_server fs/9p/vfs_addr.c:36 [inline]
v9fs_upload_to_server_worker+0x18c/0x3b0 fs/9p/vfs_addr.c:44
process_one_work+0x902/0x1a30 kernel/workqueue.c:3254
process_scheduled_works kernel/workqueue.c:3335 [inline]
worker_thread+0x6c8/0xf70 kernel/workqueue.c:3416
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>

Allocated by task 8522:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:387
kmalloc include/linux/slab.h:628 [inline]
kzalloc include/linux/slab.h:749 [inline]
p9_fid_create+0x45/0x470 net/9p/client.c:853
p9_client_walk+0xc7/0x550 net/9p/client.c:1154
clone_fid fs/9p/fid.h:23 [inline]
v9fs_fid_clone fs/9p/fid.h:33 [inline]
v9fs_file_open+0x633/0xba0 fs/9p/vfs_file.c:56
do_dentry_open+0x8da/0x18c0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x1dfb/0x2990 fs/namei.c:3799
do_filp_open+0x1dc/0x430 fs/namei.c:3826
do_sys_openat2+0x17a/0x1e0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_creat fs/open.c:1497 [inline]
__se_sys_creat fs/open.c:1491 [inline]
__ia32_sys_creat+0xcc/0x120 fs/open.c:1491
do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
__do_fast_syscall_32+0x75/0x120 arch/x86/entry/common.c:321
do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:346
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Freed by task 5209:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:579
poison_slab_object mm/kasan/common.c:240 [inline]
__kasan_slab_free+0x11d/0x1a0 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2106 [inline]
slab_free mm/slub.c:4280 [inline]
kfree+0x129/0x390 mm/slub.c:4390
p9_client_destroy+0x14c/0x480 net/9p/client.c:1070
v9fs_session_close+0x49/0x2d0 fs/9p/v9fs.c:506
v9fs_kill_super+0x4d/0xa0 fs/9p/vfs_super.c:196
deactivate_locked_super+0xbe/0x1a0 fs/super.c:472
deactivate_super+0xde/0x100 fs/super.c:505
cleanup_mnt+0x222/0x450 fs/namespace.c:1267
task_work_run+0x14e/0x250 kernel/task_work.c:180
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x278/0x2a0 kernel/entry/common.c:218
__do_fast_syscall_32+0x82/0x120 arch/x86/entry/common.c:324
do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:346
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

The buggy address belongs to the object at ffff888026991f80
which belongs to the cache kmalloc-96 of size 96
The buggy address is located 12 bytes inside of
freed 96-byte region [ffff888026991f80, ffff888026991fe0)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x26991
ksm flags: 0xfff80000000800(slab|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000800 ffff888014c42780 ffffea000077ec80 dead000000000003
raw: 0000000000000000 0000000000200020 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 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (init), ts 17747084907, free_ts 17500351980
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1534
prep_new_page mm/page_alloc.c:1541 [inline]
get_page_from_freelist+0xa28/0x3780 mm/page_alloc.c:3317
__alloc_pages+0x22b/0x2460 mm/page_alloc.c:4575
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page mm/slub.c:2175 [inline]
allocate_slab mm/slub.c:2338 [inline]
new_slab+0xcc/0x3a0 mm/slub.c:2391
___slab_alloc+0x670/0x16d0 mm/slub.c:3525
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3610
__slab_alloc_node mm/slub.c:3663 [inline]
slab_alloc_node mm/slub.c:3835 [inline]
__do_kmalloc_node mm/slub.c:3965 [inline]
__kmalloc+0x3b4/0x440 mm/slub.c:3979
kmalloc_array include/linux/slab.h:665 [inline]
kcalloc include/linux/slab.h:696 [inline]
ext4_find_extent+0x95c/0xce0 fs/ext4/extents.c:914
ext4_ext_map_blocks+0x27d/0x5ce0 fs/ext4/extents.c:4143
ext4_map_blocks+0x848/0x17d0 fs/ext4/inode.c:551
ext4_mpage_readpages+0xfef/0x1a10 fs/ext4/readpage.c:290
ext4_readahead+0x102/0x140 fs/ext4/inode.c:3143
read_pages+0x1a8/0xda0 mm/readahead.c:160
page_cache_ra_unbounded+0x450/0x5a0 mm/readahead.c:269
do_page_cache_ra mm/readahead.c:299 [inline]
page_cache_ra_order+0x64b/0x9a0 mm/readahead.c:539
ondemand_readahead+0x520/0x1140 mm/readahead.c:661
page last free pid 61 tgid 61 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1141 [inline]
free_unref_page_prepare+0x527/0xb10 mm/page_alloc.c:2347
free_unref_page+0x33/0x3c0 mm/page_alloc.c:2487
vfree+0x181/0x7a0 mm/vmalloc.c:3340
delayed_vfree_work+0x56/0x70 mm/vmalloc.c:3261
process_one_work+0x902/0x1a30 kernel/workqueue.c:3254
process_scheduled_works kernel/workqueue.c:3335 [inline]
worker_thread+0x6c8/0xf70 kernel/workqueue.c:3416
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
ffff888026991e80: 00 00 00 00 00 00 00 00 00 00 00 06 fc fc fc fc
ffff888026991f00: 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc
>ffff888026991f80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff888026992000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888026992080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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