[syzbot] [jffs2?] possible deadlock in jffs2_xattr_delete_inode
syzbot
syzbot+fdfd8fdf716c90baef0f at syzkaller.appspotmail.com
Fri Oct 23 18:44:51 PDT 2026
syzbot has found a reproducer for the following issue on:
HEAD commit: 734bef548a96 Merge tag 'net-next-7.4' of git://git.kernel...
git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=147da38e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ced4746a89083f5
dashboard link: https://syzkaller.appspot.com/bug?extid=fdfd8fdf716c90baef0f
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=167da38e580000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fdfd8fdf716c90baef0f at syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kswapd0/116 is trying to acquire lock:
ffff8880143729d8 (&c->xattr_sem){++++}-{4:4}, at: jffs2_xattr_delete_inode+0x83/0x130 fs/jffs2/xattr.c:605
but task is already holding lock:
ffffffff901caa00 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x243/0x1f00 mm/vmscan.c:7177
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (fs_reclaim){+.+.}-{0:0}:
lock_acquire kernel/locking/lockdep.c:5942 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
__fs_reclaim_acquire mm/page_alloc.c:4375 [inline]
fs_reclaim_acquire+0xc4/0x100 mm/page_alloc.c:4389
might_alloc include/linux/sched/mm.h:316 [inline]
slab_pre_alloc_hook mm/slub.c:4636 [inline]
slab_alloc_node mm/slub.c:4974 [inline]
kmem_cache_alloc_noprof+0x63/0x6a0 mm/slub.c:5010
jffs2_alloc_xattr_datum+0x1c/0xe0 fs/jffs2/malloc.c:264
create_xattr_datum fs/jffs2/xattr.c:363 [inline]
do_jffs2_setxattr+0x6f0/0x1610 fs/jffs2/xattr.c:1175
__vfs_setxattr+0x175/0x1e0 fs/xattr.c:223
__vfs_setxattr_noperm+0x127/0x660 fs/xattr.c:257
__vfs_setxattr_locked+0x127/0x2b0 fs/xattr.c:318
vfs_setxattr+0x14a/0x390 fs/xattr.c:344
do_setxattr+0x145/0x180 fs/xattr.c:662
file_setxattr fs/xattr.c:672 [inline]
file_setxattr+0x139/0x1b0 fs/xattr.c:666
path_setxattrat+0x335/0x3b0 fs/xattr.c:732
__do_sys_fsetxattr fs/xattr.c:782 [inline]
__se_sys_fsetxattr fs/xattr.c:779 [inline]
__ia32_sys_fsetxattr+0xc4/0x140 fs/xattr.c:779
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
__do_fast_syscall_32+0x14b/0x8c0 arch/x86/entry/syscall_32.c:282
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:307
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
-> #0 (&c->xattr_sem){++++}-{4:4}:
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
lock_acquire kernel/locking/lockdep.c:5942 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631
jffs2_xattr_delete_inode+0x83/0x130 fs/jffs2/xattr.c:605
jffs2_do_clear_inode+0x50/0x470 fs/jffs2/readinode.c:1418
evict+0x3c2/0xad0 fs/inode.c:822
iput_final fs/inode.c:2014 [inline]
iput.part.0+0x989/0x1050 fs/inode.c:2063
iput+0x30/0x40 fs/inode.c:2029
dentry_unlink_inode+0x403/0x4d0 fs/dcache.c:493
dentry_kill+0x25d/0xca0 fs/dcache.c:840
finish_dput fs/dcache.c:1015 [inline]
dput.part.0+0xd2/0x240 fs/dcache.c:1056
dput+0x1f/0x30 fs/dcache.c:1051
ovl_destroy_inode+0x3e/0x190 fs/overlayfs/super.c:236
destroy_inode+0xcb/0x1c0 fs/inode.c:387
evict+0x599/0xad0 fs/inode.c:846
iput_final fs/inode.c:2014 [inline]
iput.part.0+0x989/0x1050 fs/inode.c:2063
iput+0x30/0x40 fs/inode.c:2029
dentry_unlink_inode+0x403/0x4d0 fs/dcache.c:493
dentry_kill+0x25d/0xca0 fs/dcache.c:840
shrink_kill fs/dcache.c:1289 [inline]
shrink_dentry_list+0x1e8/0x310 fs/dcache.c:1306
prune_dcache_sb+0xea/0x150 fs/dcache.c:1388
super_cache_scan+0x32b/0x550 fs/super.c:225
do_shrink_slab+0x411/0x1200 mm/shrinker.c:445
shrink_slab+0x171/0x12e0 mm/shrinker.c:676
shrink_one+0x398/0x850 mm/vmscan.c:5119
shrink_many mm/vmscan.c:5180 [inline]
lru_gen_shrink_node mm/vmscan.c:5258 [inline]
shrink_node+0x2b1b/0x4310 mm/vmscan.c:6247
kswapd_shrink_node mm/vmscan.c:7101 [inline]
balance_pgdat+0xb20/0x1f00 mm/vmscan.c:7279
kswapd+0x556/0xb50 mm/vmscan.c:7555
kthread+0x373/0x450 kernel/kthread.c:436
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(fs_reclaim);
lock(&c->xattr_sem);
lock(fs_reclaim);
lock(&c->xattr_sem);
*** DEADLOCK ***
locks held by kswapd0/116: 2, last CPU#0:
#0: ffffffff901caa00 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat+0x243/0x1f00 mm/vmscan.c:7177
#1: ffff88804f2ec0e8 (&type->s_umount_key#57){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:670 [inline]
#1: ffff88804f2ec0e8 (&type->s_umount_key#57){.+.+}-{4:4}, at: super_cache_scan+0x9b/0x550 fs/super.c:200
stack backtrace:
CPU: 0 UID: 0 PID: 116 Comm: kswapd0 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
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_circular_bug.cold+0x178/0x1be kernel/locking/lockdep.c:2087
check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2219
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3209
check_prevs_add kernel/locking/lockdep.c:3328 [inline]
validate_chain kernel/locking/lockdep.c:3952 [inline]
__lock_acquire+0x1528/0x1f40 kernel/locking/lockdep.c:5288
lock_acquire kernel/locking/lockdep.c:5942 [inline]
lock_acquire+0x1d1/0x380 kernel/locking/lockdep.c:5899
down_write+0x86/0x1f0 kernel/locking/rwsem.c:1631
jffs2_xattr_delete_inode+0x83/0x130 fs/jffs2/xattr.c:605
jffs2_do_clear_inode+0x50/0x470 fs/jffs2/readinode.c:1418
evict+0x3c2/0xad0 fs/inode.c:822
iput_final fs/inode.c:2014 [inline]
iput.part.0+0x989/0x1050 fs/inode.c:2063
iput+0x30/0x40 fs/inode.c:2029
dentry_unlink_inode+0x403/0x4d0 fs/dcache.c:493
dentry_kill+0x25d/0xca0 fs/dcache.c:840
finish_dput fs/dcache.c:1015 [inline]
dput.part.0+0xd2/0x240 fs/dcache.c:1056
dput+0x1f/0x30 fs/dcache.c:1051
ovl_destroy_inode+0x3e/0x190 fs/overlayfs/super.c:236
destroy_inode+0xcb/0x1c0 fs/inode.c:387
evict+0x599/0xad0 fs/inode.c:846
iput_final fs/inode.c:2014 [inline]
iput.part.0+0x989/0x1050 fs/inode.c:2063
iput+0x30/0x40 fs/inode.c:2029
dentry_unlink_inode+0x403/0x4d0 fs/dcache.c:493
dentry_kill+0x25d/0xca0 fs/dcache.c:840
shrink_kill fs/dcache.c:1289 [inline]
shrink_dentry_list+0x1e8/0x310 fs/dcache.c:1306
prune_dcache_sb+0xea/0x150 fs/dcache.c:1388
super_cache_scan+0x32b/0x550 fs/super.c:225
do_shrink_slab+0x411/0x1200 mm/shrinker.c:445
shrink_slab+0x171/0x12e0 mm/shrinker.c:676
shrink_one+0x398/0x850 mm/vmscan.c:5119
shrink_many mm/vmscan.c:5180 [inline]
lru_gen_shrink_node mm/vmscan.c:5258 [inline]
shrink_node+0x2b1b/0x4310 mm/vmscan.c:6247
kswapd_shrink_node mm/vmscan.c:7101 [inline]
balance_pgdat+0xb20/0x1f00 mm/vmscan.c:7279
kswapd+0x556/0xb50 mm/vmscan.c:7555
kthread+0x373/0x450 kernel/kthread.c:436
ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
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.
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