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From 34407a175a59b668a1a2bbf0d0e495d87a7777d8 Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Wed, 1 Aug 2018 10:37:16 +0800
Subject: [PATCH] btrfs: Check that each block group has corresponding chunk at
mount time
commit 514c7dca85a0bf40be984dab0b477403a6db901f upstream.
A crafted btrfs image with incorrect chunk<->block group mapping will
trigger a lot of unexpected things as the mapping is essential.
Although the problem can be caught by block group item checker
added in "btrfs: tree-checker: Verify block_group_item", it's still not
sufficient. A sufficiently valid block group item can pass the check
added by the mentioned patch but could fail to match the existing chunk.
This patch will add extra block group -> chunk mapping check, to ensure
we have a completely matching (start, len, flags) chunk for each block
group at mount time.
Here we reuse the original helper find_first_block_group(), which is
already doing the basic bg -> chunk checks, adding further checks of the
start/len and type flags.
CVE: CVE-2018-14610
Upstream-Status: Backport
Link: https://bugzilla.kernel.org/show_bug.cgi?id=199837
Reported-by: Xu Wen <wen.xu@gatech.edu>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
fs/btrfs/extent-tree.c | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index fdc42eddccc2..83791d13c204 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -9828,6 +9828,8 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info,
int ret = 0;
struct btrfs_key found_key;
struct extent_buffer *leaf;
+ struct btrfs_block_group_item bg;
+ u64 flags;
int slot;
ret = btrfs_search_slot(NULL, root, key, path, 0, 0);
@@ -9862,8 +9864,32 @@ static int find_first_block_group(struct btrfs_fs_info *fs_info,
"logical %llu len %llu found bg but no related chunk",
found_key.objectid, found_key.offset);
ret = -ENOENT;
+ } else if (em->start != found_key.objectid ||
+ em->len != found_key.offset) {
+ btrfs_err(fs_info,
+ "block group %llu len %llu mismatch with chunk %llu len %llu",
+ found_key.objectid, found_key.offset,
+ em->start, em->len);
+ ret = -EUCLEAN;
} else {
- ret = 0;
+ read_extent_buffer(leaf, &bg,
+ btrfs_item_ptr_offset(leaf, slot),
+ sizeof(bg));
+ flags = btrfs_block_group_flags(&bg) &
+ BTRFS_BLOCK_GROUP_TYPE_MASK;
+
+ if (flags != (em->map_lookup->type &
+ BTRFS_BLOCK_GROUP_TYPE_MASK)) {
+ btrfs_err(fs_info,
+"block group %llu len %llu type flags 0x%llx mismatch with chunk type flags 0x%llx",
+ found_key.objectid,
+ found_key.offset, flags,
+ (BTRFS_BLOCK_GROUP_TYPE_MASK &
+ em->map_lookup->type));
+ ret = -EUCLEAN;
+ } else {
+ ret = 0;
+ }
}
free_extent_map(em);
goto out;
--
2.19.2
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