ext4: fix journal credit check when setting fscrypt context

Fix an issue arising when ext4 features has_journal, ea_inode, and encrypt are activated simultaneously, leading to ENOSPC when creating an encrypted file.

Fix by passing XATTR_CREATE flag to xattr_set_handle function if a handle is specified, i.e., when the function is called in the control flow of creating a new inode. This aligns the number of jbd2 credits set_handle checks for with the number allocated for creating a new inode.

ext4_set_context must not be called with a non-null handle (fs_data) if fscrypt context xattr is not guaranteed to not exist yet. The only other usage of this function currently is when handling the ioctl FS_IOC_SET_ENCRYPTION_POLICY, which calls it with fs_data=NULL.

---
 fs/ext4/crypto.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

index cf0a0970c095..a89a14dffa48 100644
@@ -163,10 +163,15 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
 	 */
 
 	if (handle) {
+		/*
+		 * Since the inode is new it is ok to pass the XATTR_CREATE flag. This
+		 * is necessary to match the reamining journal credits check in the
+		 * set_handle function with the credits allocated for the new inode.
+		 */
 		res = ext4_xattr_set_handle(handle, inode,
 					    EXT4_XATTR_INDEX_ENCRYPTION,
 					    EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
-					    ctx, len, 0);
+					    ctx, len, XATTR_CREATE);
 		if (!res) {
 			ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
 			ext4_clear_inode_state(inode,

2.49.0

Hi Eric,

thanks for your approval.

How do we continue from here? Do I have to resubmit a patch with the typo fixed or can it just be fixed on the maintainer's side? If I resubmit, I should include your Reviewed-by tag at the bottom, correct?

Cheers,
Simon

This should get taken through the ext4 tree eventually. You don't need to resend the patch just for a typo and Reviewed-by.

- Eric

Applied, thanks!

[1/1] ext4: fix journal credit check when setting fscrypt context

      commit: cb8c10c17a8b339423cd950a04841c5b3287f346

Best regards,

Theodore Ts'o <[email protected]>