When accessing a file with more entries than ES_MAX_ENTRY_NUM, the bh-array is allocated in __exfat_get_entry_set. The problem is that the bh-array is allocated with GFP_KERNEL. It does not make sense. In the following cases, a deadlock for sbi->s_lock between the two processes may occur.

CPU0 CPU1 ---- ---- kswapd balance_pgdat lock(fs_reclaim) exfat_iterate lock(&sbi->s_lock) exfat_readdir exfat_get_uniname_from_ext_entry exfat_get_dentry_set __exfat_get_dentry_set kmalloc_array ... lock(fs_reclaim) ... evict exfat_evict_inode lock(&sbi->s_lock)

To fix this, let's allocate bh-array with GFP_NOFS.

Fixes: a3ff29a95fde ("exfat: support dynamic allocate bh for exfat_entry_set_cache") Cc: stable@vger.kernel.org # v6.2+ Reported-by: syzbot+412a392a2cd4a65e71db@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/000000000000fef47e0618c0327f@google.com Signed-off-by: Sungjong Seo sj1557.seo@samsung.com --- fs/exfat/dir.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/exfat/dir.c b/fs/exfat/dir.c index 84572e11cc05..7446bf09a04a 100644 --- a/fs/exfat/dir.c +++ b/fs/exfat/dir.c @@ -813,7 +813,7 @@ static int __exfat_get_dentry_set(struct exfat_entry_set_cache *es,

num_bh = EXFAT_B_TO_BLK_ROUND_UP(off + num_entries * DENTRY_SIZE, sb); if (num_bh > ARRAY_SIZE(es->__bh)) { - es->bh = kmalloc_array(num_bh, sizeof(*es->bh), GFP_KERNEL); + es->bh = kmalloc_array(num_bh, sizeof(*es->bh), GFP_NOFS); if (!es->bh) { brelse(bh); return -ENOMEM;