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exfat: fix reporting fs error when reading dir beyond EOF

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Since seekdir() does not check whether the position is valid, the
position may exceed the size of the directory. We found that for
a directory with discontinuous clusters, if the position exceeds
the size of the directory and the excess size is greater than or
equal to the cluster size, exfat_readdir() will return -EIO,
causing a file system error and making the file system unavailable.

Reproduce this bug by:

seekdir(dir, dir_size + cluster_size);
dirent = readdir(dir);

The following log will be printed if mount with 'errors=remount-ro'.

[11166.712896] exFAT-fs (sdb1): error, invalid access to FAT (entry 0xffffffff)
[11166.712905] exFAT-fs (sdb1): Filesystem has been set read-only

Fixes: 1e5654de0f ("exfat: handle wrong stream entry size in exfat_readdir()")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Reviewed-by: Andy Wu <Andy.Wu@sony.com>
Reviewed-by: Aoyama Wataru <wataru.aoyama@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 2022-10-20 14:27:37 +08:00 committed by Namjae Jeon
parent 6cb5d1a16a
commit 706fdcac00
1 changed files with 1 additions and 1 deletions
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2
fs/exfat/dir.c
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@ -100,7 +100,7 @@ static int exfat_readdir(struct inode *inode, loff_t *cpos, struct exfat_dir_ent
clu.dir = ei->hint_bmap.clu;
}
while (clu_offset > 0) {
while (clu_offset > 0 && clu.dir != EXFAT_EOF_CLUSTER) {
if (exfat_get_next_cluster(sb, &(clu.dir)))
return -EIO;