Fix squashfs failing to load sparse files
SquashFS supports sprase blocks in files - that is, if a given block is
composed only of zeros, it's not written to the output file to save
space and it's on-disk length field is set to zero to indicate that.
Previously the squashfs driver did not recognise that, and would attempt
to read and decompress a zero-sized block, which obviously failed.
The following command may be used to create a file for testing:
cat <(dd if=/dev/urandom of=/dev/stdout bs=1M count=1) \
<(dd if=/dev/zero of=/dev/stdout bs=1M count=1) \
<(dd if=/dev/urandom of=/dev/stdout bs=1k count=200) >test_file
Signed-off-by: Campbell Suter <campbell@snapit.group>
diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
index 5de69ac..dca13bd 100644
--- a/fs/squashfs/sqfs.c
+++ b/fs/squashfs/sqfs.c
@@ -1310,7 +1310,7 @@
{
char *dir = NULL, *fragment_block, *datablock = NULL, *data_buffer = NULL;
char *fragment = NULL, *file = NULL, *resolved, *data;
- u64 start, n_blks, table_size, data_offset, table_offset;
+ u64 start, n_blks, table_size, data_offset, table_offset, sparse_size;
int ret, j, i_number, datablk_count = 0;
struct squashfs_super_block *sblk = ctxt.sblk;
struct squashfs_fragment_block_entry frag_entry;
@@ -1444,28 +1444,43 @@
n_blks = DIV_ROUND_UP(table_size + table_offset,
ctxt.cur_dev->blksz);
- data_buffer = malloc_cache_aligned(n_blks * ctxt.cur_dev->blksz);
+ /* Don't load any data for sparse blocks */
+ if (finfo.blk_sizes[j] == 0) {
+ n_blks = 0;
+ table_offset = 0;
+ data_buffer = NULL;
+ data = NULL;
+ } else {
+ data_buffer = malloc_cache_aligned(n_blks * ctxt.cur_dev->blksz);
- if (!data_buffer) {
- ret = -ENOMEM;
- goto out;
- }
+ if (!data_buffer) {
+ ret = -ENOMEM;
+ goto out;
+ }
- ret = sqfs_disk_read(start, n_blks, data_buffer);
- if (ret < 0) {
- /*
- * Possible causes: too many data blocks or too large
- * SquashFS block size. Tip: re-compile the SquashFS
- * image with mksquashfs's -b <block_size> option.
- */
- printf("Error: too many data blocks to be read.\n");
- goto out;
- }
+ ret = sqfs_disk_read(start, n_blks, data_buffer);
+ if (ret < 0) {
+ /*
+ * Possible causes: too many data blocks or too large
+ * SquashFS block size. Tip: re-compile the SquashFS
+ * image with mksquashfs's -b <block_size> option.
+ */
+ printf("Error: too many data blocks to be read.\n");
+ goto out;
+ }
- data = data_buffer + table_offset;
+ data = data_buffer + table_offset;
+ }
/* Load the data */
- if (SQFS_COMPRESSED_BLOCK(finfo.blk_sizes[j])) {
+ if (finfo.blk_sizes[j] == 0) {
+ /* This is a sparse block */
+ sparse_size = get_unaligned_le32(&sblk->block_size);
+ if ((*actread + sparse_size) > len)
+ sparse_size = len - *actread;
+ memset(buf + *actread, 0, sparse_size);
+ *actread += sparse_size;
+ } else if (SQFS_COMPRESSED_BLOCK(finfo.blk_sizes[j])) {
dest_len = get_unaligned_le32(&sblk->block_size);
ret = sqfs_decompress(&ctxt, datablock, &dest_len,
data, table_size);
@@ -1484,7 +1499,8 @@
}
data_offset += table_size;
- free(data_buffer);
+ if (data_buffer)
+ free(data_buffer);
data_buffer = NULL;
if (*actread >= len)
break;