Re: [PATCH] fs/squashfs: fix reading of fragmented files

Le 17/05/2021 à 23:20, Joao Marcos Costa a écrit :

The fragmented files were not correctly read because of two issues:

• The squashfs_file_info struct has a field named 'comp', which tells if

the file's fragment is compressed or not. This field was always set to 'true' in sqfs_get_regfile_info and sqfs_get_lregfile_info. It should actually take sqfs_frag_lookup's return value. This patch addresses these two assignments.

• In sqfs_read, the fragments (compressed or not) were copied to the

output buffer through a for loop which was reading data at the wrong offset. Replace these loops by equivalent calls to memcpy, with the right parameters.

I tested this patch by comparing the MD5 checksum of a few fragmented files with the respective md5sum output in sandbox, considering both compressed and uncompressed fragments.

Signed-off-by: Joao Marcos Costa jmcosta944@gmail.com

Tested-by: Richard Genoud richard.genoud@posteo.net

Tested it on real hardware, with mksquashfs -always-use-fragments, loading a kernel (fit) from squashfs. It wasn't working before the patch, and works after.

Thanks !

---

fs/squashfs/sqfs.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c index 29805c3c6f..22ef4f2691 100644 --- a/fs/squashfs/sqfs.c +++ b/fs/squashfs/sqfs.c @@ -1253,7 +1253,7 @@ static int sqfs_get_regfile_info(struct squashfs_reg_inode *reg, fentry); if (ret < 0) return -EINVAL;

• finfo->comp = true;
  

• finfo->comp = ret;
  

  if (fentry->size < 1 || fentry->start == 0x7FFFFFFF) return -EINVAL; } else {

@@ -1291,7 +1291,7 @@ static int sqfs_get_lregfile_info(struct squashfs_lreg_inode *lreg, fentry); if (ret < 0) return -EINVAL;

• finfo->comp = true;
  

• finfo->comp = ret;
  

  if (fentry->size < 1 || fentry->start == 0x7FFFFFFF) return -EINVAL; } else {

@@ -1547,20 +1547,16 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len, goto out; }

• for (j = *actread; j < finfo.size; j++) {
  

• 	memcpy(buf + j, &fragment_block[finfo.offset + j], 1);
  

• 	(*actread)++;
  

• }
  

• memcpy(buf + *actread, &fragment_block[finfo.offset], finfo.size - *actread);
  

• *actread = finfo.size;
  
  

  free(fragment_block);

  } else if (finfo.frag && !finfo.comp) { fragment_block = (void *)fragment + table_offset;

• for (j = *actread; j < finfo.size; j++) {
  

• 	memcpy(buf + j, &fragment_block[finfo.offset + j], 1);
  

• 	(*actread)++;
  

• }
  

• memcpy(buf + *actread, &fragment_block[finfo.offset], finfo.size - *actread);
  

• *actread = finfo.size;
  

  }

  out: