2023-07-14 17:43 GMT+09:00, Sungjong Seo sj1557.seo@samsung.com:
There is a potential deadlock reported by syzbot as below:
====================================================== WARNING: possible circular locking dependency detected 6.4.0-next-20230707-syzkaller #0 Not tainted
syz-executor330/5073 is trying to acquire lock: ffff8880218527a0 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock_killable include/linux/mmap_lock.h:151 [inline] ffff8880218527a0 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5293 [inline] ffff8880218527a0 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x369/0x510 mm/memory.c:5344 but task is already holding lock: ffff888019f760e0 (&sbi->s_lock){+.+.}-{3:3}, at: exfat_iterate+0x117/0xb50 fs/exfat/dir.c:232
which lock already depends on the new lock.
Chain exists of: &mm->mmap_lock --> mapping.invalidate_lock#3 --> &sbi->s_lock
Possible unsafe locking scenario:
CPU0 CPU1 ---- ----lock(&sbi->s_lock); lock(mapping.invalidate_lock#3); lock(&sbi->s_lock); rlock(&mm->mmap_lock);
Let's try to avoid above potential deadlock condition by moving dir_emit*() out of sbi->s_lock coverage.
Fixes: ca06197382bd ("exfat: add directory operations") Cc: stable@vger.kernel.org #v5.7+ Reported-by: syzbot+1741a5d9b79989c10bdc@syzkaller.appspotmail.com Link: https://lore.kernel.org/lkml/00000000000078ee7e060066270b@google.com/T/#u Signed-off-by: Sungjong Seo sj1557.seo@samsung.com
Applied it to #dev, Thanks for your patch!