github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-11-07 06:17:02 +01:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

exfat: fix reading a directory whose FAT chain is longer than its size

Browse Source 
Commit 08cf4a8181 ("exfat: use exfat_chain_advance helper") made the
directory code walk the clusters of a directory with
exfat_chain_advance().

However, exfat_chain_advance() returns -EIO once it has walked as many
clusters as the size of the directory says. The FAT chain of a directory
can be longer than that, because some cameras stop updating the size,
see commit 1e5654de0f ("exfat: handle wrong stream entry size in
exfat_readdir()"). As of now, opening such a directory fails with EIO as
soon as the chain is two clusters longer than the size. Reading a
directory that has a FAT chain after a seek past its end fails with EIO
too.

The issue can be reproduced with an image in which the size of a
directory with 200 files and 7 clusters is lowered to 2 clusters:

    mount -o loop exfat.img /mnt
    ls /mnt/d | wc -l

Before commit 08cf4a8181 ("exfat: use exfat_chain_advance helper"),
the result is:

    200

After that commit, ls fails with "Input/output error" and the result is:

    0

This patch will make exfat_chain_advance() follow the FAT to its end
when the directory has a FAT chain, as the code did before, and keep the
size check for a directory without one.

Fixes: 08cf4a8181 ("exfat: use exfat_chain_advance helper")
Cc: stable@vger.kernel.org
Signed-off-by: Hengyu Liang <hengyul@cs.unc.edu>
Reviewed-by: Chi Zhiling <chizhiling@kylinos.cn>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Hengyu Liang 2026-10-15 10:49:34 -04:00 committed by Namjae Jeon
parent b4c282c0d8
commit 8534eb11ac
1 changed files with 19 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
fs/exfat/exfat_fs.h
View File

@ -680,19 +680,29 @@ static inline int exfat_chain_advance(struct super_block *sb,
struct exfat_chain *chain, unsigned int step)
{
unsigned int clu = chain->dir;
unsigned int i;
if (unlikely(chain->size < step))
return -EIO;
if (chain->flags == ALLOC_NO_FAT_CHAIN) {
if (unlikely(chain->size < step))
return -EIO;
if (exfat_cluster_walk(sb, &clu, step, chain->flags))
return -EIO;
chain->size -= step;
chain->dir = chain->size ? clu + step : EXFAT_EOF_CLUSTER;
return 0;
}
chain->size -= step;
/*
* Only the FAT tells where a chain of this kind ends. The size can be
* smaller than the chain, see commit 1e5654de0f51 ("exfat: handle
* wrong stream entry size in exfat_readdir()").
*/
for (i = 0; i < step && clu != EXFAT_EOF_CLUSTER; i++) {
if (exfat_get_next_cluster(sb, &clu))
return -EIO;
}
if (chain->size == 0 && chain->flags == ALLOC_NO_FAT_CHAIN)
chain->dir = EXFAT_EOF_CLUSTER;
else
chain->dir = clu;
chain->size -= min(chain->size, step);
chain->dir = clu;
return 0;
}