[PATCH 2/2] ext4: reject encrypted inodes when block size > page size

[Alberto Garcia <berto@igalia.com>]

Encryption is not supported when a filesystem's block size is larger
than the page size. ext4_check_large_folio() refuses to mount a
filesystem like that if the "encrypt" feature is already enabled, and
ext4_set_context() refuses to create encrypted inodes if the feature
is enabled after mounting.

However, a corrupted or hand-crafted filesystem can still have
encrypted inodes even if the "encrypt" feature is not set, and those
inodes can be unlocked if they're using v1 policies.

Check this in __ext4_iget() and reject them as corrupted.

Fixes: 709f0f1f1bf5 ("ext4: add checks for large folio incompatibilities when BS > PS")
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Alberto Garcia <berto@igalia.com>
---
 fs/ext4/inode.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 26f0f9714f03..31248fef8bce 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5671,6 +5671,12 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
 		ret = -EFSCORRUPTED;
 		goto bad_inode;
 	}
+	if (IS_ENCRYPTED(inode) && sb->s_blocksize > PAGE_SIZE) {
+		ext4_error_inode(inode, function, line, 0,
+				 "encrypted inode with block size larger than page size");
+		ret = -EFSCORRUPTED;
+		goto bad_inode;
+	}
 
 	ext4_set_inode_mapping_order(inode);
 
-- 
2.47.3