[SRU Focal, Bionic PATCH 2/2] ext4: fix check for block being out of directory size

[Cengiz Can]

From: Jan Kara <jack at suse.cz>

The check in __ext4_read_dirblock() for block being outside of directory
size was wrong because it compared block number against directory size
in bytes. Fix it.

Fixes: 65f8ea4cd57d ("ext4: check if directory block is within i_size")
CVE: CVE-2022-1184
CC: stable at vger.kernel.org
Signed-off-by: Jan Kara <jack at suse.cz>
Reviewed-by: Lukas Czerner <lczerner at redhat.com>
Link: https://lore.kernel.org/r/20220822114832.1482-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso at mit.edu>
CVE-2022-1184
(cherry picked from commit 61a1d87a324ad5e3ed27c6699dfc93218fcf3201)
Signed-off-by: Cengiz Can <cengiz.can at canonical.com>
---
 fs/ext4/namei.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index f8faf6d742cd..9c49764fb9ef 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -123,7 +123,7 @@ static struct buffer_head *__ext4_read_dirblock(struct inode *inode,
 	struct ext4_dir_entry *dirent;
 	int is_dx_block = 0;
 
-	if (block >= inode->i_size) {
+	if (block >= inode->i_size >> inode->i_blkbits) {
 		ext4_error_inode(inode, func, line, block,
 		       "Attempting to read directory block (%u) that is past i_size (%llu)",
 		       block, inode->i_size);
-- 
2.39.2