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

Commit 08cf4a8181b4 ("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 1e5654de0f51 ("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 08cf4a8181b4 ("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: 08cf4a8181b4 ("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>

0 files changed, 0 insertions, 0 deletions