Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to avoid potential deadlock

As Jiaming Zhang and syzbot reported, there is potential deadlock in f2fs as below:

Chain exists of: &sbi->cp_rwsem --> fs_reclaim --> sb_internal#2

Possible unsafe locking scenario:

CPU0 CPU1 ---- ---- rlock(sb_internal#2); lock(fs_reclaim); lock(sb_internal#2); rlock(&sbi->cp_rwsem);

*** DEADLOCK ***

3 locks held by kswapd0/73: #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:7015 [inline] #0: ffffffff8e247a40 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0x951/0x2800 mm/vmscan.c:7389 #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_trylock_shared fs/super.c:562 [inline] #1: ffff8880118400e0 (&type->s_umount_key#50){.+.+}-{4:4}, at: super_cache_scan+0x91/0x4b0 fs/super.c:197 #2: ffff888011840610 (sb_internal#2){.+.+}-{0:0}, at: f2fs_evict_inode+0x8d9/0x1b60 fs/f2fs/inode.c:890

stack backtrace: CPU: 0 UID: 0 PID: 73 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~bpo12+1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2043 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165…