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Subject[PATCH 4.14 41/63] ext4: make sanity check in mballoc more strict
Date
From: Jan Kara <jack@suse.cz>

commit 31562b954b60f02acb91b7349dc6432d3f8c3c5f upstream.

The sanity check in mb_find_extent() only checked that returned extent
does not extend past blocksize * 8, however it should not extend past
EXT4_CLUSTERS_PER_GROUP(sb). This can happen when clusters_per_group <
blocksize * 8 and the tail of the bitmap is not properly filled by 1s
which happened e.g. when ancient kernels have grown the filesystem.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/ext4/mballoc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -1555,7 +1555,7 @@ static int mb_find_extent(struct ext4_bu
ex->fe_len += 1 << order;
}

- if (ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3))) {
+ if (ex->fe_start + ex->fe_len > EXT4_CLUSTERS_PER_GROUP(e4b->bd_sb)) {
/* Should never happen! (but apparently sometimes does?!?) */
WARN_ON(1);
ext4_error(e4b->bd_sb, "corruption or bug in mb_find_extent "

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