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authorCampbell Suter <campbell@snapit.group>2020-11-23 15:40:03 +1300
committerTom Rini <trini@konsulko.com>2021-01-20 14:01:44 -0500
commit9dba07f14304612ed4ee6d827898aa0cb55d4e26 (patch)
tree993e262d50a903b112a025f4e5d169407476fa81 /fs
parent3b72612ad191cad29aad3982221ff3355bec798d (diff)
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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>
Diffstat (limited to 'fs')
-rw-r--r--fs/squashfs/sqfs.c54
1 files changed, 35 insertions, 19 deletions
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 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
{
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 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
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 @@ int sqfs_read(const char *filename, void *buf, loff_t offset, loff_t len,
}
data_offset += table_size;
- free(data_buffer);
+ if (data_buffer)
+ free(data_buffer);
data_buffer = NULL;
if (*actread >= len)
break;