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exfat: fix the infinite loop in exfat_readdir()

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If the file system is corrupted so that a cluster is linked to
itself in the cluster chain, and there is an unused directory
entry in the cluster, 'dentry' will not be incremented, causing
condition 'dentry < max_dentries' unable to prevent an infinite
loop.

This infinite loop causes s_lock not to be released, and other
tasks will hang, such as exfat_sync_fs().

This commit stops traversing the cluster chain when there is unused
directory entry in the cluster to avoid this infinite loop.

Reported-by: syzbot+205c2644abdff9d3f9fc@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=205c2644abdff9d3f9fc
Tested-by: syzbot+205c2644abdff9d3f9fc@syzkaller.appspotmail.com
Fixes: ca06197382 ("exfat: add directory operations")
Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Yuezhang Mo 2024-12-13 13:08:37 +08:00 committed by Namjae Jeon
parent ffee32cf4b
commit 4265319f10
1 changed files with 2 additions and 1 deletions
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3
fs/exfat/dir.c
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@ -122,7 +122,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent
type = exfat_get_entry_type(ep);
if (type == TYPE_UNUSED) {
brelse(bh);
break;
goto out;
}
if (type != TYPE_FILE && type != TYPE_DIR) {
@ -170,6 +170,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent
}
}
out:
dir_entry->namebuf.lfn[0] = '\0';
*cpos = EXFAT_DEN_TO_B(dentry);
return 0;