Remove compressor internal buffers

Pass in an external destination buffer + size and allow for propper
bounds checking (especially when unpacking).

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

4 files changed, 21 insertions, 8 deletions

diff --git a/lib/sqfs/frag_reader.c b/lib/sqfs/frag_reader.c
index 1906376..74fd292 100644
--- a/lib/sqfs/frag_reader.c
+++ b/lib/sqfs/frag_reader.c
@@ -42,12 +42,15 @@ static int precache_block(frag_reader_t *f, size_t i)
 	}
 
 	if (compressed) {
-		ret = f->cmp->do_block(f->cmp, f->buffer, size);
+		ret = f->cmp->do_block(f->cmp, f->buffer, size,
+				       f->buffer + f->block_size, f->block_size);
 
 		if (ret <= 0) {
 			fputs("extracting fragment failed\n", stderr);
 			return -1;
 		}
+
+		memmove(f->buffer, f->buffer + f->block_size, ret);
 	}
 
 	f->current_index = i;
@@ -73,7 +76,7 @@ frag_reader_t *frag_reader_create(sqfs_super_t *super, int fd,
 		++blockcount;
 
 	/* pre allocate all the stuff */
-	f = calloc(1, sizeof(*f) + super->block_size);
+	f = calloc(1, sizeof(*f) + super->block_size * 2);
 	if (f == NULL)
 		goto fail_rd;
 
diff --git a/lib/sqfs/meta_reader.c b/lib/sqfs/meta_reader.c
index 8cd7c8f..1a70238 100644
--- a/lib/sqfs/meta_reader.c
+++ b/lib/sqfs/meta_reader.c
@@ -79,12 +79,18 @@ int meta_reader_seek(meta_reader_t *m, uint64_t block_start, size_t offset)
 		goto fail_trunc;
 
 	if (compressed) {
-		ret = m->cmp->do_block(m->cmp, m->data, size);
+		ret = m->cmp->do_block(m->cmp, m->data, size,
+				       m->scratch, sizeof(m->scratch));
 
 		if (ret <= 0) {
 			fputs("error uncompressing meta data block\n", stderr);
 			return -1;
 		}
+
+		memcpy(m->data, m->scratch, ret);
+
+		if ((size_t)ret < sizeof(m->data))
+			memset(m->data + ret, 0, sizeof(m->data) - ret);
 	}
 
 	return 0;
diff --git a/lib/sqfs/meta_writer.c b/lib/sqfs/meta_writer.c
index 95092d5..77ceeb9 100644
--- a/lib/sqfs/meta_writer.c
+++ b/lib/sqfs/meta_writer.c
@@ -30,23 +30,27 @@ void meta_writer_destroy(meta_writer_t *m)
 int meta_writer_flush(meta_writer_t *m)
 {
 	ssize_t ret, count;
+	void *ptr;
 
 	if (m->offset == 0)
 		return 0;
 
-	ret = m->cmp->do_block(m->cmp, m->data + 2, m->offset);
+	ret = m->cmp->do_block(m->cmp, m->data + 2, m->offset,
+			       m->scratch + 2, sizeof(m->scratch) - 2);
 	if (ret < 0)
 		return -1;
 
 	if (ret > 0) {
-		((uint16_t *)m->data)[0] = htole16(ret);
+		((uint16_t *)m->scratch)[0] = htole16(ret);
 		count = ret + 2;
+		ptr = m->scratch;
 	} else {
 		((uint16_t *)m->data)[0] = htole16(m->offset | 0x8000);
 		count = m->offset + 2;
+		ptr = m->data;
 	}
 
-	ret = write_retry(m->outfd, m->data, count);
+	ret = write_retry(m->outfd, ptr, count);
 
 	if (ret < 0) {
 		perror("writing meta data");
diff --git a/lib/sqfs/super.c b/lib/sqfs/super.c
index b402496..d3b79c6 100644
--- a/lib/sqfs/super.c
+++ b/lib/sqfs/super.c
@@ -17,8 +17,8 @@ int sqfs_super_init(sqfs_super_t *super, size_t block_size, uint32_t mtime,
 		return -1;
 	}
 
-	if (block_size < 8192 || block_size >= (1 << 24)) {
-		fputs("Block size must be between 8k and 1M\n", stderr);
+	if (block_size < 4096 || block_size >= (1 << 24)) {
+		fputs("Block size must be between 4k and 1M\n", stderr);
 		return -1;
 	}