From 3a7845041eb7235f2fb00ef0960995da5be63b11 Mon Sep 17 00:00:00 2001 From: Yuezhang Mo Date: Fri, 16 Feb 2024 20:19:55 +0800 Subject: [PATCH] exfat: fix appending discontinuous clusters to empty file Eric Hong found that when using ftruncate to expand an empty file, exfat_ent_set() will fail if discontinuous clusters are allocated. The reason is that the empty file does not have a cluster chain, but exfat_ent_set() attempts to append the newly allocated cluster to the cluster chain. In addition, exfat_find_last_cluster() only supports finding the last cluster in a non-empty file. So this commit adds a check whether the file is empty. If the file is empty, exfat_find_last_cluster() and exfat_ent_set() are no longer called as they do not need to be called. Fixes: f55c096f62f1 ("exfat: do not zero the extended part") Reported-by: Eric Hong Signed-off-by: Yuezhang Mo Signed-off-by: Namjae Jeon --- fs/exfat/file.c | 35 +++++++++++++++++++++-------------- 1 file changed, 21 insertions(+), 14 deletions(-) diff --git a/fs/exfat/file.c b/fs/exfat/file.c index d25a96a148af..cc00f1a7a1e1 100644 --- a/fs/exfat/file.c +++ b/fs/exfat/file.c @@ -35,13 +35,18 @@ static int exfat_cont_expand(struct inode *inode, loff_t size) if (new_num_clusters == num_clusters) goto out; - exfat_chain_set(&clu, ei->start_clu, num_clusters, ei->flags); - ret = exfat_find_last_cluster(sb, &clu, &last_clu); - if (ret) - return ret; + if (num_clusters) { + exfat_chain_set(&clu, ei->start_clu, num_clusters, ei->flags); + ret = exfat_find_last_cluster(sb, &clu, &last_clu); + if (ret) + return ret; + + clu.dir = last_clu + 1; + } else { + last_clu = EXFAT_EOF_CLUSTER; + clu.dir = EXFAT_EOF_CLUSTER; + } - clu.dir = (last_clu == EXFAT_EOF_CLUSTER) ? - EXFAT_EOF_CLUSTER : last_clu + 1; clu.size = 0; clu.flags = ei->flags; @@ -51,17 +56,19 @@ static int exfat_cont_expand(struct inode *inode, loff_t size) return ret; /* Append new clusters to chain */ - if (clu.flags != ei->flags) { - exfat_chain_cont_cluster(sb, ei->start_clu, num_clusters); - ei->flags = ALLOC_FAT_CHAIN; - } - if (clu.flags == ALLOC_FAT_CHAIN) - if (exfat_ent_set(sb, last_clu, clu.dir)) - goto free_clu; + if (num_clusters) { + if (clu.flags != ei->flags) + if (exfat_chain_cont_cluster(sb, ei->start_clu, num_clusters)) + goto free_clu; - if (num_clusters == 0) + if (clu.flags == ALLOC_FAT_CHAIN) + if (exfat_ent_set(sb, last_clu, clu.dir)) + goto free_clu; + } else ei->start_clu = clu.dir; + ei->flags = clu.flags; + out: inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode)); /* Expanded range not zeroed, do not update valid_size */