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authorTheodore Ts'o <tytso@mit.edu>2018-06-14 00:58:00 -0400
committerTheodore Ts'o <tytso@mit.edu>2018-06-14 00:58:00 -0400
commit8844618d8aa7a9973e7b527d038a2a589665002c (patch)
tree73e3eeb52d03d548d6cab2c600984f07a72b9e10 /fs/ext4/balloc.c
parent77260807d1170a8cf35dbb06e07461a655f67eee (diff)
ext4: only look at the bg_flags field if it is valid
The bg_flags field in the block group descripts is only valid if the uninit_bg or metadata_csum feature is enabled. We were not consistently looking at this field; fix this. Also block group #0 must never have uninitialized allocation bitmaps, or need to be zeroed, since that's where the root inode, and other special inodes are set up. Check for these conditions and mark the file system as corrupted if they are detected. This addresses CVE-2018-10876. https://bugzilla.kernel.org/show_bug.cgi?id=199403 Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org
Diffstat (limited to 'fs/ext4/balloc.c')
-rw-r--r--fs/ext4/balloc.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 8a2e202ade8a..e68cefe08261 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -438,7 +438,16 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
goto verify;
}
ext4_lock_group(sb, block_group);
- if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
+ if (ext4_has_group_desc_csum(sb) &&
+ (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT))) {
+ if (block_group == 0) {
+ ext4_unlock_group(sb, block_group);
+ unlock_buffer(bh);
+ ext4_error(sb, "Block bitmap for bg 0 marked "
+ "uninitialized");
+ err = -EFSCORRUPTED;
+ goto out;
+ }
err = ext4_init_block_bitmap(sb, bh, block_group, desc);
set_bitmap_uptodate(bh);
set_buffer_uptodate(bh);