[syzbot] possible deadlock in exfat_iterate

From: syzbot
Date: Tue Oct 04 2022 - 11:23:47 EST

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Hello,

syzbot found the following issue on:

HEAD commit: bbed346d5a96 Merge branch 'for-next/core' into for-kernelci
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=12781dbc880000
kernel config: https://syzkaller.appspot.com/x/.config?x=aae2d21e7dd80684
dashboard link: https://syzkaller.appspot.com/bug?extid=38655f1298fefc58a904
compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/11078f50b80b/disk-bbed346d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/398e5f1e6c84/vmlinux-bbed346d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+38655f1298fefc58a904@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0 Not tainted
------------------------------------------------------
syz-executor.5/7308 is trying to acquire lock:
ffff000109945b58 (&mm->mmap_lock){++++}-{3:3}, at: __might_fault+0x54/0xb4 mm/memory.c:5576

but task is already holding lock:
ffff00010d89e0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_iterate+0x74/0xcd8 fs/exfat/dir.c:228

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #2 (&sbi->s_lock#2){+.+.}-{3:3}:
__mutex_lock_common+0xd4/0xca8 kernel/locking/mutex.c:603
__mutex_lock kernel/locking/mutex.c:747 [inline]
mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
exfat_get_block+0x6c/0x9ec fs/exfat/inode.c:282
do_mpage_readpage+0x474/0xd38 fs/mpage.c:208
mpage_readahead+0xf0/0x1b8 fs/mpage.c:361
exfat_readahead+0x28/0x38 fs/exfat/inode.c:345
read_pages+0x74/0x4a0 mm/readahead.c:158
page_cache_ra_unbounded+0x2cc/0x338 mm/readahead.c:263
do_page_cache_ra mm/readahead.c:293 [inline]
page_cache_ra_order+0x348/0x380 mm/readahead.c:550
ondemand_readahead+0x3cc/0x724 mm/readahead.c:672
page_cache_sync_ra+0xc4/0xdc mm/readahead.c:699
page_cache_sync_readahead include/linux/pagemap.h:1215 [inline]
filemap_get_pages+0x108/0x574 mm/filemap.c:2566
filemap_read+0x14c/0x6fc mm/filemap.c:2660
generic_file_read_iter+0x6c/0x25c mm/filemap.c:2806
call_read_iter include/linux/fs.h:2181 [inline]
generic_file_splice_read+0xa0/0x1c8 fs/splice.c:309
do_splice_to fs/splice.c:793 [inline]
splice_direct_to_actor+0x16c/0x3e4 fs/splice.c:865
do_splice_direct+0xc4/0x14c fs/splice.c:974
do_sendfile+0x298/0x68c fs/read_write.c:1249
__do_sys_sendfile64 fs/read_write.c:1317 [inline]
__se_sys_sendfile64 fs/read_write.c:1303 [inline]
__arm64_sys_sendfile64+0xb0/0x230 fs/read_write.c:1303
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

-> #1 (mapping.invalidate_lock#3){.+.+}-{3:3}:
down_read+0x5c/0x78 kernel/locking/rwsem.c:1499
filemap_invalidate_lock_shared include/linux/fs.h:811 [inline]
filemap_fault+0x104/0x804 mm/filemap.c:3112
__do_fault+0x60/0x358 mm/memory.c:4173
do_read_fault mm/memory.c:4518 [inline]
do_fault+0x338/0x550 mm/memory.c:4647
handle_pte_fault mm/memory.c:4911 [inline]
__handle_mm_fault mm/memory.c:5053 [inline]
handle_mm_fault+0x784/0xa40 mm/memory.c:5151
__do_page_fault arch/arm64/mm/fault.c:502 [inline]
do_page_fault+0x428/0x79c arch/arm64/mm/fault.c:602
do_translation_fault+0x78/0x194 arch/arm64/mm/fault.c:685
do_mem_abort+0x54/0x130 arch/arm64/mm/fault.c:821
el1_abort+0x3c/0x5c arch/arm64/kernel/entry-common.c:366
el1h_64_sync_handler+0x60/0xac arch/arm64/kernel/entry-common.c:426
el1h_64_sync+0x64/0x68 arch/arm64/kernel/entry.S:576
do_strncpy_from_user lib/strncpy_from_user.c:41 [inline]
strncpy_from_user+0x1a8/0x3d8 lib/strncpy_from_user.c:139
getname_flags+0x84/0x278 fs/namei.c:150
getname+0x28/0x38 fs/namei.c:218
do_sys_openat2+0x78/0x22c fs/open.c:1307
do_sys_open fs/open.c:1329 [inline]
__do_sys_openat fs/open.c:1345 [inline]
__se_sys_openat fs/open.c:1340 [inline]
__arm64_sys_openat+0xb0/0xe0 fs/open.c:1340
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

-> #0 (&mm->mmap_lock){++++}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x1530/0x30a4 kernel/locking/lockdep.c:5053
lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666
__might_fault+0x7c/0xb4 mm/memory.c:5577
filldir64+0x1e4/0x56c fs/readdir.c:335
dir_emit_dot include/linux/fs.h:3547 [inline]
dir_emit_dots include/linux/fs.h:3558 [inline]
exfat_iterate+0xd8/0xcd8 fs/exfat/dir.c:231
iterate_dir+0x114/0x28c
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x80/0x204 fs/readdir.c:354
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

other info that might help us debug this:

Chain exists of:
&mm->mmap_lock --> mapping.invalidate_lock#3 --> &sbi->s_lock#2

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sbi->s_lock#2);
lock(mapping.invalidate_lock#3);
lock(&sbi->s_lock#2);
lock(&mm->mmap_lock);

*** DEADLOCK ***

3 locks held by syz-executor.5/7308:
#0: ffff0000c71e8ce8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x12c/0x154 fs/file.c:1036
#1: ffff0001091738f8 (&sb->s_type->i_mutex_key#21){++++}-{3:3}, at: iterate_dir+0xb8/0x28c fs/readdir.c:57
#2: ffff00010d89e0e0 (&sbi->s_lock#2){+.+.}-{3:3}, at: exfat_iterate+0x74/0xcd8 fs/exfat/dir.c:228

stack backtrace:
CPU: 1 PID: 7308 Comm: syz-executor.5 Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
Call trace:
dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:156
show_stack+0x2c/0x54 arch/arm64/kernel/stacktrace.c:163
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x104/0x16c lib/dump_stack.c:106
dump_stack+0x1c/0x58 lib/dump_stack.c:113
print_circular_bug+0x2c4/0x2c8 kernel/locking/lockdep.c:2053
check_noncircular+0x14c/0x154 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3095 [inline]
check_prevs_add kernel/locking/lockdep.c:3214 [inline]
validate_chain kernel/locking/lockdep.c:3829 [inline]
__lock_acquire+0x1530/0x30a4 kernel/locking/lockdep.c:5053
lock_acquire+0x100/0x1f8 kernel/locking/lockdep.c:5666
__might_fault+0x7c/0xb4 mm/memory.c:5577
filldir64+0x1e4/0x56c fs/readdir.c:335
dir_emit_dot include/linux/fs.h:3547 [inline]
dir_emit_dots include/linux/fs.h:3558 [inline]
exfat_iterate+0xd8/0xcd8 fs/exfat/dir.c:231
iterate_dir+0x114/0x28c
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64 fs/readdir.c:354 [inline]
__arm64_sys_getdents64+0x80/0x204 fs/readdir.c:354
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581

---
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Next message: Sean Anderson: "Re: [PATCH net-next v6 5/9] net: fman: memac: Use lynx pcs driver"
Previous message: Juergen Gross: "Re: [PATCH v2 1/3] xen/pv: allow pmu msr accesses to cause GP"
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