btrfs-progs: Detect compressed extent without csum

There is one report of compressed extent happens in btrfs, but has no csum and then leads to possible decompress error screwing up kernel memory.

Although it's a kernel bug, and won't cause problem until compressed data get corrupted, let's catch such problem in advance.

This patch will catch any unexpected compressed extent with:

1) 0 or less than expected csum

2) nodatasum flag set in the inode item

This is for lowmem mode.

Reported-by James Harvey <[email protected]>

Issue: #134

Signed-off-by Qu Wenruo <[email protected]>

---
 check/mode-lowmem.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

check/mode-lowmem.c +18 -0

index dac3201b7d99..8e6d5e8de12a 100644
@@ -1543,6 +1543,24 @@ static int check_file_extent(struct btrfs_root *root, struct btrfs_key *fkey,
 			      csum_found);
 		}
 	}
+	/*
+	 * Extra check for compressed extents.
+	 * Btrfs doesn't allow NODATASUM and compressed extent co-exist, thus
+	 * all compressed extent should have csum.
+	 */
+	if (compressed && csum_found < search_len) {
+		error(
+"root %llu EXTENT_DATA[%llu %llu] compressed extent must have csum, but only %llu bytes has csum, expect %llu",
+		      root->objectid, fkey->objectid, fkey->offset, csum_found,
+		      search_len);
+		err |= CSUM_ITEM_MISSING;
+	}
+	if (compressed && nodatasum) {
+		error(
+"root %llu EXTENT_DATA[%llu %llu] is compressed, but inode flag doesn't allow it",
+		      root->objectid, fkey->objectid, fkey->offset);
+		err |= FILE_EXTENT_ERROR;
+	}
 
 	/* Check EXTENT_DATA hole */
 	if (!no_holes && *end != fkey->offset) {

There is one report of compressed extent happens in btrfs, but has no csum and then leads to possible decompress error screwing up kernel memory.

Although it's a kernel bug, and won't cause problem until compressed data get corrupted, let's catch such problem in advance.

This patch will catch any unexpected compressed extent with:

1) 0 or less than expected csum

2) nodatasum flag set in the inode item

This is for original mode.

Reported-by James Harvey <[email protected]>

Issue: #134

Signed-off-by Qu Wenruo <[email protected]>

---
 check/main.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

check/main.c +8 -2

index 891a6d797756..db064b27e84b 100644
@@ -1437,6 +1437,7 @@ static int process_file_extent(struct btrfs_root *root,
 	u64 mask = root->fs_info->sectorsize - 1;
 	u32 max_inline_size = min_t(u32, mask,
 				BTRFS_MAX_INLINE_DATA_SIZE(root->fs_info));
+	u8 compression;
 	int extent_type;
 	int ret;
 

@@ -1460,9 +1461,9 @@ static int process_file_extent(struct btrfs_root *root,
 
 	fi = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
 	extent_type = btrfs_file_extent_type(eb, fi);
+	compression = btrfs_file_extent_compression(eb, fi);
 
 	if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
-		u8 compression = btrfs_file_extent_compression(eb, fi);
 		struct btrfs_item *item = btrfs_item_nr(slot);
 
 		num_bytes = btrfs_file_extent_inline_len(eb, slot, fi);

@@ -1494,6 +1495,8 @@ static int process_file_extent(struct btrfs_root *root,
 		     btrfs_file_extent_encryption(eb, fi) ||
 		     btrfs_file_extent_other_encoding(eb, fi)))
 			rec->errors |= I_ERR_BAD_FILE_EXTENT;
+		if (compression && rec->nodatasum)
+			rec->errors |= I_ERR_BAD_FILE_EXTENT;
 		if (disk_bytenr > 0)
 			rec->found_size += num_bytes;
 	} else {

@@ -1512,7 +1515,8 @@ static int process_file_extent(struct btrfs_root *root,
 	if (disk_bytenr > 0 &&
 	    btrfs_header_owner(eb) != BTRFS_DATA_RELOC_TREE_OBJECTID) {
 		u64 found;
-		if (btrfs_file_extent_compression(eb, fi))
+
+		if (compression)
 			num_bytes = btrfs_file_extent_disk_num_bytes(eb, fi);
 		else
 			disk_bytenr += extent_offset;

@@ -1526,6 +1530,8 @@ static int process_file_extent(struct btrfs_root *root,
 				rec->found_csum_item = 1;
 			if (found < num_bytes)
 				rec->some_csum_missing = 1;
+			if (compression && found < num_bytes)
+				rec->errors |= I_ERR_SOME_CSUM_MISSING;
 		} else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
 			if (found > 0) {
 				ret = check_prealloc_extent_written(root->fs_info,