Re: [syzbot] [netfs?] kernel BUG in netfs_limit_iter

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in netfs_limit_iter

------------[ cut here ]------------
kernel BUG at fs/netfs/iterator.c:248!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 1 UID: 0 PID: 6595 Comm: syz.0.28 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 d8 3d 74 fe e9 59 f6 ff ff e8 8e e6 b1 ff e9 6f f6 ff ff e8 64 69 45 ff 90 <0f> 0b e8 ec e5 b1 ff e9 cd f9 ff ff 4c 89 f6 48 c7 c7 20 dc ab 8e
RSP: 0018:ffffc90003c16c70 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82c33b2b
RDX: ffff88802b2aa4c0 RSI: ffffffff82c34a5c RDI: ffff88802b2aa4c0
RBP: 0000000000000003 R08: 0000000000000001 R09: 0000000000000005
R10: 0000000000000003 R11: 0000000000000012 R12: 000000007fffffff
R13: 1ffff92000782d94 R14: ffff88802222ef60 R15: ffff8880224b2580
FS:  00007ffbb60b56c0(0000) GS:ffff8880d6444000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffea0531a80 CR3: 000000002ff66000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 netfs_unbuffered_write+0x2bb/0x2290 fs/netfs/direct_write.c:128
 netfs_unbuffered_write_iter_locked+0x801/0xab0 fs/netfs/direct_write.c:295
 netfs_unbuffered_write_iter+0x40c/0x710 fs/netfs/direct_write.c:385
 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: 00007ffbb5415fa0 RCX: 00007ffbb519c799
RDX: 0000000000000000 RSI: 0000200000000080 RDI: 0000000000008000
RBP: 00007ffbb5232bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007ffbb5416038 R14: 00007ffbb5415fa0 R15: 00007ffea05320b8
 </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 d8 3d 74 fe e9 59 f6 ff ff e8 8e e6 b1 ff e9 6f f6 ff ff e8 64 69 45 ff 90 <0f> 0b e8 ec e5 b1 ff e9 cd f9 ff ff 4c 89 f6 48 c7 c7 20 dc ab 8e
RSP: 0018:ffffc90003c16c70 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82c33b2b
RDX: ffff88802b2aa4c0 RSI: ffffffff82c34a5c RDI: ffff88802b2aa4c0
RBP: 0000000000000003 R08: 0000000000000001 R09: 0000000000000005
R10: 0000000000000003 R11: 0000000000000012 R12: 000000007fffffff
R13: 1ffff92000782d94 R14: ffff88802222ef60 R15: ffff8880224b2580
FS:  00007ffbb60b56c0(0000) GS:ffff8880d6644000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffea0530cd0 CR3: 000000002ff66000 CR4: 0000000000352ef0


Tested on:

commit:         c107785c Merge tag 'modules-7.0-rc3.fixes' of git://gi..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=103ad8d6580000
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
patch:          https://syzkaller.appspot.com/x/patch.diff?x=131ad8d6580000