[PATCH 3.16 048/245] btrfs: tree-checker: Verify block_group_item

Ben Hutchings
2020-04-23T23:21:43Z

From: Qu Wenruo <wqu@suse.com>

commit fce466eab7ac6baa9d2dcd88abcf945be3d4a089 upstream.

A crafted image with invalid block group items could make free space cache
code to cause panic.

We could detect such invalid block group item by checking:
1) Item size
Known fixed value.
2) Block group size (key.offset)
We have an upper limit on block group item (10G)
3) Chunk objectid
Known fixed value.
4) Type
Only 4 valid type values, DATA, METADATA, SYSTEM and DATA|METADATA.
No more than 1 bit set for profile type.
5) Used space
No more than the block group size.

This should allow btrfs to detect and refuse to mount the crafted image.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=199849
Reported-by: Xu Wen <wen.xu@gatech.edu>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Gu Jinxiang <gujx@cn.fujitsu.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Gu Jinxiang <gujx@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
[bwh: Backported to 4.4:
- In check_leaf_item(), pass root->fs_info to check_block_group_item()
- Include <linux/sizes.h> (in ctree.h, to match upstream)
- Adjust context]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/ctree.h | 1 +
fs/btrfs/tree-checker.c | 100 ++++++++++++++++++++++++++++++++++++++++
fs/btrfs/volumes.c | 2 +-
fs/btrfs/volumes.h | 2 +
4 files changed, 104 insertions(+), 1 deletion(-)

--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -34,6 +34,7 @@
#include <linux/pagemap.h>
#include <linux/btrfs.h>
#include <linux/workqueue.h>
+#include <linux/sizes.h>
#include "extent_io.h"
#include "extent_map.h"
#include "async-thread.h"
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -31,6 +31,7 @@
#include "disk-io.h"
#include "compression.h"
#include "hash.h"
+#include "volumes.h"

#define CORRUPT(reason, eb, root, slot) \
btrfs_crit(root->fs_info, \
@@ -312,6 +313,102 @@ static int check_dir_item(struct btrfs_r
return 0;
}

+__printf(4, 5)
+__cold
+static void block_group_err(const struct btrfs_fs_info *fs_info,
+ const struct extent_buffer *eb, int slot,
+ const char *fmt, ...)
+{
+ struct btrfs_key key;
+ struct va_format vaf;
+ va_list args;
+
+ btrfs_item_key_to_cpu(eb, &key, slot);
+ va_start(args, fmt);
+
+ vaf.fmt = fmt;
+ vaf.va = &args;
+
+ btrfs_crit(fs_info,
+ "corrupt %s: root=%llu block=%llu slot=%d bg_start=%llu bg_len=%llu, %pV",
+ btrfs_header_level(eb) == 0 ? "leaf" : "node",
+ btrfs_header_owner(eb), btrfs_header_bytenr(eb), slot,
+ key.objectid, key.offset, &vaf);
+ va_end(args);
+}
+
+static int check_block_group_item(struct btrfs_fs_info *fs_info,
+ struct extent_buffer *leaf,
+ struct btrfs_key *key, int slot)
+{
+ struct btrfs_block_group_item bgi;
+ u32 item_size = btrfs_item_size_nr(leaf, slot);
+ u64 flags;
+ u64 type;
+
+ /*
+ * Here we don't really care about alignment since extent allocator can
+ * handle it. We care more about the size, as if one block group is
+ * larger than maximum size, it's must be some obvious corruption.
+ */
+ if (key->offset > BTRFS_MAX_DATA_CHUNK_SIZE || key->offset == 0) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group size, have %llu expect (0, %llu]",
+ key->offset, BTRFS_MAX_DATA_CHUNK_SIZE);
+ return -EUCLEAN;
+ }
+
+ if (item_size != sizeof(bgi)) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid item size, have %u expect %zu",
+ item_size, sizeof(bgi));
+ return -EUCLEAN;
+ }
+
+ read_extent_buffer(leaf, &bgi, btrfs_item_ptr_offset(leaf, slot),
+ sizeof(bgi));
+ if (btrfs_block_group_chunk_objectid(&bgi) !=
+ BTRFS_FIRST_CHUNK_TREE_OBJECTID) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group chunk objectid, have %llu expect %llu",
+ btrfs_block_group_chunk_objectid(&bgi),
+ BTRFS_FIRST_CHUNK_TREE_OBJECTID);
+ return -EUCLEAN;
+ }
+
+ if (btrfs_block_group_used(&bgi) > key->offset) {
+ block_group_err(fs_info, leaf, slot,
+ "invalid block group used, have %llu expect [0, %llu)",
+ btrfs_block_group_used(&bgi), key->offset);
+ return -EUCLEAN;
+ }
+
+ flags = btrfs_block_group_flags(&bgi);
+ if (hweight64(flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) > 1) {
+ block_group_err(fs_info, leaf, slot,
+"invalid profile flags, have 0x%llx (%lu bits set) expect no more than 1 bit set",
+ flags & BTRFS_BLOCK_GROUP_PROFILE_MASK,
+ hweight64(flags & BTRFS_BLOCK_GROUP_PROFILE_MASK));
+ return -EUCLEAN;
+ }
+
+ type = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
+ if (type != BTRFS_BLOCK_GROUP_DATA &&
+ type != BTRFS_BLOCK_GROUP_METADATA &&
+ type != BTRFS_BLOCK_GROUP_SYSTEM &&
+ type != (BTRFS_BLOCK_GROUP_METADATA |
+ BTRFS_BLOCK_GROUP_DATA)) {
+ block_group_err(fs_info, leaf, slot,
+"invalid type, have 0x%llx (%lu bits set) expect either 0x%llx, 0x%llx, 0x%llu or 0x%llx",
+ type, hweight64(type),
+ BTRFS_BLOCK_GROUP_DATA, BTRFS_BLOCK_GROUP_METADATA,
+ BTRFS_BLOCK_GROUP_SYSTEM,
+ BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA);
+ return -EUCLEAN;
+ }
+ return 0;
+}
+
/*
* Common point to switch the item-specific validation.
*/
@@ -333,6 +430,9 @@ static int check_leaf_item(struct btrfs_
case BTRFS_XATTR_ITEM_KEY:
ret = check_dir_item(root, leaf, key, slot);
break;
+ case BTRFS_BLOCK_GROUP_ITEM_KEY:
+ ret = check_block_group_item(root->fs_info, leaf, key, slot);
+ break;
}
return ret;
}
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4134,7 +4134,7 @@ static int __btrfs_alloc_chunk(struct bt

if (type & BTRFS_BLOCK_GROUP_DATA) {
max_stripe_size = 1024 * 1024 * 1024;
- max_chunk_size = 10 * max_stripe_size;
+ max_chunk_size = BTRFS_MAX_DATA_CHUNK_SIZE;
if (!devs_max)
devs_max = BTRFS_MAX_DEVS(info->chunk_root);
} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -24,6 +24,8 @@
#include <linux/btrfs.h>
#include "async-thread.h"

+#define BTRFS_MAX_DATA_CHUNK_SIZE (10ULL * SZ_1G)
+
#define BTRFS_STRIPE_LEN (64 * 1024)

struct buffer_head;