linux-kernel - task hung in exfat_write

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Date: Thu, 21 Dec 2023 14:11:05 +0800
From: Lizhi Xu <lizhi.xu@...driver.com>
To: <syzbot+2f73ed585f115e98aee8@...kaller.appspotmail.com>
CC: <linux-kernel@...r.kernel.org>, <syzkaller-bugs@...glegroups.com>
Subject: task hung in exfat_write_inode

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f9ff5644bcc0

diff --git a/fs/exfat/fatent.c b/fs/exfat/fatent.c
index 56b870d9cc0d..2908eb82fe68 100644
--- a/fs/exfat/fatent.c
+++ b/fs/exfat/fatent.c
@@ -149,7 +149,7 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 {
 	struct super_block *sb = inode->i_sb;
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
-	int cur_cmap_i, next_cmap_i;
+	int cur_cmap_i, next_cmap_i, ei = 0;
 	unsigned int num_clusters = 0;
 	unsigned int clu;
 
@@ -176,8 +176,11 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 
 	if (p_chain->flags == ALLOC_NO_FAT_CHAIN) {
 		unsigned int last_cluster = p_chain->dir + p_chain->size - 1;
+		printk("b dir: %u, s: %u, nc: %u\n", p_chain->dir, p_chain->size, num_clusters);
 		do {
 			bool sync = false;
+			if (ei > 100)
+				break;
 
 			if (clu < last_cluster)
 				next_cmap_i =
@@ -192,12 +195,17 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 			exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
 			clu++;
 			num_clusters++;
+			ei++;
 		} while (num_clusters < p_chain->size);
+		printk("e dir: %u, s: %u, nc: %u, e: %d\n", p_chain->dir, p_chain->size, num_clusters, ei);
 	} else {
+		printk("b2 dir: %u, s: %u, nc: %u\n", p_chain->dir, p_chain->size, num_clusters);
 		do {
 			bool sync = false;
 			unsigned int n_clu = clu;
 			int err = exfat_get_next_cluster(sb, &n_clu);
+			if (ei > 100)
+				break;
 
 			if (err || n_clu == EXFAT_EOF_CLUSTER)
 				sync = true;
@@ -213,10 +221,12 @@ static int __exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain
 			exfat_clear_bitmap(inode, clu, (sync && IS_DIRSYNC(inode)));
 			clu = n_clu;
 			num_clusters++;
+			ei++;
 
 			if (err)
 				goto dec_used_clus;
 		} while (clu != EXFAT_EOF_CLUSTER);
+		printk("e2 dir: %u, s: %u, nc: %u, e: %d\n", p_chain->dir, p_chain->size, num_clusters, ei);
 	}
 
 dec_used_clus:
@@ -229,8 +239,10 @@ int exfat_free_cluster(struct inode *inode, struct exfat_chain *p_chain)
 	int ret = 0;
 
 	mutex_lock(&EXFAT_SB(inode->i_sb)->bitmap_lock);
+	printk("i: %p, %s\n", inode, __func__);
 	ret = __exfat_free_cluster(inode, p_chain);
 	mutex_unlock(&EXFAT_SB(inode->i_sb)->bitmap_lock);
+	printk("r: %d, i: %p, %s\n", ret, inode, __func__);
 
 	return ret;
 }