Re: [PATCH 1/2] ext4: refuse encryption when block size > page size

[Baokun Li <libaokun@linux.alibaba.com>]

On 2026/9/25 22:19, Alberto Garcia wrote:
> Encryption is not supported when a filesystem's block size is larger
> than the page size, and commit 709f0f1f1bf5 ("ext4: add checks for
> large folio incompatibilities when BS > PS") added a check to refuse
> mounting such a filesystem.
>
> However, it is also possible to enable the "encrypt" feature on a
> filesystem that is already mounted (with tune2fs -O encrypt). Once
> that happens it won't be possible to mount the filesystem again in
> the future, but there is nothing preventing the user from setting an
> encryption policy while the filesystem is still mounted.
>
> Fix this by refusing to set an fscrypt context in ext4_set_context()
> when the block size is larger than the page size.
>
> Fixes: 709f0f1f1bf5 ("ext4: add checks for large folio incompatibilities when BS > PS")
> Cc: stable@vger.kernel.org # v6.19+
> Signed-off-by: Alberto Garcia <berto@igalia.com>


Thanks for the patch, feel free to add:

Reviewed-by: Baokun Li <libaokun@linux.alibaba.com>

> ---
>  fs/ext4/crypto.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
> index 1a0fccb084ef..318b2eaea741 100644
> --- a/fs/ext4/crypto.c
> +++ b/fs/ext4/crypto.c
> @@ -156,6 +156,15 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
>  	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX))
>  		return -EOPNOTSUPP;
>  
> +	/*
> +	 * Encryption is not supported when the block size is larger
> +	 * than the page size.  This is rejected at mount time by
> +	 * ext4_check_large_folio(), and this check here is for the case
> +	 * when the 'encrypt' feature is enabled on a mounted filesystem.
> +	 */
> +	if (inode->i_sb->s_blocksize > PAGE_SIZE)
> +		return -EOPNOTSUPP;
> +
>  	res = ext4_convert_inline_data(inode);
>  	if (res)
>  		return res;