[syzbot] [netfs?] kernel BUG in netfs_limit_iter

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c107785c7e8d Merge tag 'modules-7.0-rc3.fixes' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13d408ba580000
kernel config: https://syzkaller.appspot.com/x/.config?x=976ba5a93c4add9e
dashboard link: https://syzkaller.appspot.com/bug?extid=9c058f0d63475adc97fd
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16421552580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=166a97e6580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-c107785c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3a4a4abcd973/vmlinux-c107785c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f60667f16840/bzImage-c107785c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9c058f...@syzkaller.appspotmail.com

------------[ cut here ]------------
kernel BUG at fs/netfs/iterator.c:248!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 6437 Comm: syz.9.39 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:netfs_limit_iter+0x100d/0x1100 fs/netfs/iterator.c:248
Code: ff e9 a4 f4 ff ff 48 89 de 48 c7 c7 a0 db ab 8e e8 e8 3f 74 fe e9 59 f6 ff ff e8 9e e8 b1 ff e9 6f f6 ff ff e8 74 6b 45 ff 90 <0f> 0b e8 fc e7 b1 ff e9 cd f9 ff ff 4c 89 f6 48 c7 c7 20 dc ab 8e
RSP: 0018:ffffc900040e6d18 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82c3391b
RDX: ffff8880298a0000 RSI: ffffffff82c3484c RDI: ffff8880298a0000
RBP: 0000000000000003 R08: 0000000000000001 R09: 0000000000000005
R10: 0000000000000003 R11: 0000000000000012 R12: 000000007fffffff
R13: 1ffff9200081cda9 R14: ffff88801c7f3960 R15: ffff888022886580
FS: 000055556085f500(0000) GS:ffff8880d6644000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008fdc000 CR3: 000000002f279000 CR4: 0000000000352ef0
Call Trace:
<TASK>
netfs_unbuffered_write+0x25d/0x2080 fs/netfs/direct_write.c:128
netfs_unbuffered_write_iter_locked+0x801/0xab0 fs/netfs/direct_write.c:287
netfs_unbuffered_write_iter+0x40c/0x710 fs/netfs/direct_write.c:377
v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
__kernel_write_iter+0x2ac/0x920 fs/read_write.c:621
__kernel_write+0xf6/0x140 fs/read_write.c:641
__dump_emit fs/coredump.c:1221 [inline]
dump_emit+0x21f/0x330 fs/coredump.c:1259
elf_core_dump+0x2127/0x3d10 fs/binfmt_elf.c:2062
coredump_write fs/coredump.c:1050 [inline]
do_coredump fs/coredump.c:1127 [inline]
vfs_coredump+0x27bc/0x5570 fs/coredump.c:1201
get_signal+0x1f2a/0x21e0 kernel/signal.c:3019
arch_do_signal_or_restart+0x91/0x7a0 arch/x86/kernel/signal.c:337
__exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
exit_to_user_mode_loop kernel/entry/common.c:98 [inline]
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
irqentry_exit+0x1f8/0x670 kernel/entry/common.c:219
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 002b:0000200000000088 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f5120e15fa0 RCX: 00007f5120b9c799
RDX: 0000000000000000 RSI: 0000200000000080 RDI: 0000000000008000
RBP: 00007f5120c32bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f5120e15fac R14: 00007f5120e15fa0 R15: 00007f5120e15fa0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:netfs_limit_iter+0x100d/0x1100 fs/netfs/iterator.c:248
Code: ff e9 a4 f4 ff ff 48 89 de 48 c7 c7 a0 db ab 8e e8 e8 3f 74 fe e9 59 f6 ff ff e8 9e e8 b1 ff e9 6f f6 ff ff e8 74 6b 45 ff 90 <0f> 0b e8 fc e7 b1 ff e9 cd f9 ff ff 4c 89 f6 48 c7 c7 20 dc ab 8e
RSP: 0018:ffffc900040e6d18 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82c3391b
RDX: ffff8880298a0000 RSI: ffffffff82c3484c RDI: ffff8880298a0000
RBP: 0000000000000003 R08: 0000000000000001 R09: 0000000000000005
R10: 0000000000000003 R11: 0000000000000012 R12: 000000007fffffff
R13: 1ffff9200081cda9 R14: ffff88801c7f3960 R15: ffff888022886580
FS: 000055556085f500(0000) GS:ffff8880d6644000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008fdc000 CR3: 000000002f279000 CR4: 0000000000352ef0


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup