[syzbot] [netfs?] WARNING: refcount bug in netfs_put_subrequest

[syzbot <syzbot+d9890527385ab9767e03@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    69b54314c975 Merge tag 'kbuild-fixes-v6.14' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=106d6bdf980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a7ddf49cf33ba213
dashboard link: https://syzkaller.appspot.com/bug?extid=d9890527385ab9767e03
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13aafdf8580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-69b54314.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2d0a58d1d655/vmlinux-69b54314.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b99949b40299/bzImage-69b54314.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d9890527385ab9767e03@syzkaller.appspotmail.com

netfs: Couldn't get user pages (rc=-14)
------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 6306 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 UID: 0 PID: 6306 Comm: syz.2.100 Not tainted 6.14.0-rc1-syzkaller-00276-g69b54314c975 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 78 71 f5 fc 84 db 0f 85 66 ff ff ff e8 cb 76 f5 fc c6 05 e5 68 86 0b 01 90 48 c7 c7 00 fb d2 8b e8 97 b2 b5 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 a8 76 f5 fc 0f b6 1d c0 68 86 0b 31
RSP: 0018:ffffc900030d7750 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817a1159
RDX: ffff88805135c880 RSI: ffffffff817a1166 RDI: 0000000000000001
RBP: ffff88802d916fa0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000005
R13: 000000000000006f R14: 0000000000000001 R15: ffff88802d916fa0
FS:  00007fee79bce6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fee79bad000 CR3: 00000000233ec000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:275 [inline]
 __refcount_dec_and_test include/linux/refcount.h:307 [inline]
 netfs_put_subrequest+0x2c1/0x4d0 fs/netfs/objects.c:230
 netfs_collect_read_results fs/netfs/read_collect.c:300 [inline]
 netfs_read_collection+0x25af/0x3cb0 fs/netfs/read_collect.c:417
 netfs_wait_for_pause+0x31c/0x3e0 fs/netfs/read_collect.c:689
 netfs_dispatch_unbuffered_reads fs/netfs/direct_read.c:106 [inline]
 netfs_unbuffered_read fs/netfs/direct_read.c:144 [inline]
 netfs_unbuffered_read_iter_locked+0xb50/0x1610 fs/netfs/direct_read.c:229
 netfs_unbuffered_read_iter+0xc5/0x100 fs/netfs/direct_read.c:264
 v9fs_file_read_iter+0xbf/0x100 fs/9p/vfs_file.c:361
 aio_read+0x313/0x4e0 fs/aio.c:1602
 __io_submit_one fs/aio.c:2003 [inline]
 io_submit_one+0x1580/0x1da0 fs/aio.c:2052
 __do_sys_io_submit fs/aio.c:2111 [inline]
 __se_sys_io_submit fs/aio.c:2081 [inline]
 __x64_sys_io_submit+0x1b2/0x340 fs/aio.c:2081
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fee78d8cde9
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:00007fee79bce038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d1
RAX: ffffffffffffffda RBX: 00007fee78fa5fa0 RCX: 00007fee78d8cde9
RDX: 00004000000002c0 RSI: 0000000000000001 RDI: 00007fee79bad000
RBP: 00007fee78e0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fee78fa5fa0 R15: 00007ffe1e525b98
 </TASK>


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