[PATCH] erofs-utils: fsck: fix segmentation fault for file extraction

[Gao Xiang]

On 2023/6/5 20:58, Guo Xuenan via Linux-erofs wrote:
> Currently, we use fsckcfg.extract_path to record the path of file
> to be extracted, when the name is too long, it will exceed the
> fsckcfg.extract_path[PATH_MAX] array and segmentation fault may
> occur.
> 
> Test and reproduce with the following script:
> ``` bash
> #!/bin/bash
> FSCK=`which fsck.erofs`
> MKFS=`which mkfs.erofs`
> 
> IN_DIR=./src
> $MKFS x.img ${IN_DIR}
> 
> get_dst_dir()
> {
> 	local len=$1
> 	local perlen=$2
> 	local dst_dir=$(printf 'a%.0s' $(seq 1 $((perlen - 1))))
> 	local n=$((len / ${perlen}))
> 	local lastlen=$((len - perlen * n))
> 	local lastdir=$(printf 'a%.0s' $(seq 1 $lastlen))
> 	local outdir=""
> 	for x in `seq 1 $n`
> 	do
> 		outdir=${outdir}/${dst_dir}
> 	done
> 
> 	[[ -n $lastdir ]] && outdir=${outdir}/${lastdir}
> 	echo ${outdir}
> }
> 
> for n in `seq 4000 1 5000`
> do
> 	dst_dir=$(get_dst_dir $n 255)
> 	echo ${#dst_dir}
> 
> 	OUT_DIR="./${dst_dir}"
> 	rm -rf $(dirname $OUT_DIR) > /dev/null 2>&1
> 	mkdir -p $OUT_DIR
> 	$FSCK --extract=${OUT_DIR} x.img > /dev/null 2>&1
> done
> ```
> 
> Fixes: f44043561491 ("erofs-utils: introduce fsck.erofs")
> Fixes: b11f84f593f9 ("erofs-utils: fsck: convert to use erofs_iterate_dir()")
> Fixes: 412c8f908132 ("erofs-utils: fsck: add --extract=X support to extract to path X")
> Signed-off-by: Guo Xuenan <guoxuenan at huawei.com>

Reviewed-by: Gao Xiang <hsiangkao at linux.alibaba.com>

Thanks,
Gao Xiang