Merge: ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find()

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/4601

JIRA: https://issues.redhat.com/browse/RHEL-45031

CVE: CVE-2024-39276
 
Signed-off-by: Pavel Reichl <preichl@redhat.com>

Approved-by: Andrey Albershteyn <aalbersh@redhat.com>
Approved-by: Bill O'Donnell <bodonnel@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Lucas Zampieri <lzampier@redhat.com>

Author: zampierilucas

fs/ext4/xattr.c

@@ -3113,8 +3113,10 @@ ext4_xattr_block_cache_find(struct inode *inode,
 
 		bh = ext4_sb_bread(inode->i_sb, ce->e_value, REQ_PRIO);
 		if (IS_ERR(bh)) {
-			if (PTR_ERR(bh) == -ENOMEM)
+			if (PTR_ERR(bh) == -ENOMEM) {
+				mb_cache_entry_put(ea_block_cache, ce);
 				return NULL;
+			}
 			bh = NULL;
 			EXT4_ERROR_INODE(inode, "block %lu read error",
 					 (unsigned long)ce->e_value);