From 21313279887dba506b42eeb55a8e497d69efa17d Mon Sep 17 00:00:00 2001 From: Yuezhang Mo Date: Fri, 1 Mar 2024 20:23:44 +0900 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 --- file.c | 37 ++++++++++++++++++++++--------------- 1 file changed, 22 insertions(+), 15 deletions(-) diff --git a/file.c b/file.c index 34a9a55..43faa0f 100644 --- a/file.c +++ b/file.c @@ -37,13 +37,18 @@ 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; @@ -53,17 +58,19 @@ 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 == 0) + if (num_clusters) { + if (clu.flags != ei->flags) + if (exfat_chain_cont_cluster(sb, ei->start_clu, num_clusters)) + goto free_clu; + + 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: #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 6, 0) #if LINUX_VERSION_CODE >= KERNEL_VERSION(6, 7, 0)