ACK: [CVE-2018-11412][Bionic][SRU][PATCH 1/1] ext4: do not allow external inodes for inline data

[Kleber Souza]

On 07/26/18 10:41, Po-Hsu Lin wrote:
> From: Theodore Ts'o <tytso at mit.edu>
> 
> CVE-2018-11412
> 
> The inline data feature was implemented before we added support for
> external inodes for xattrs.  It makes no sense to support that
> combination, but the problem is that there are a number of extended
> attribute checks that are skipped if e_value_inum is non-zero.
> 
> Unfortunately, the inline data code is completely e_value_inum
> unaware, and attempts to interpret the xattr fields as if it were an
> inline xattr --- at which point, Hilarty Ensues.
> 
> This addresses CVE-2018-11412.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=199803
> 
> Reported-by: Jann Horn <jannh at google.com>
> Reviewed-by: Andreas Dilger <adilger at dilger.ca>
> Signed-off-by: Theodore Ts'o <tytso at mit.edu>
> Fixes: e50e5129f384 ("ext4: xattr-in-inode support")
> Cc: stable at kernel.org
> (cherry picked from commit 117166efb1ee8f13c38f9e96b258f16d4923f888)
> Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>

> ---
>  fs/ext4/inline.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/fs/ext4/inline.c b/fs/ext4/inline.c
> index 1367553c43bb..1e10eb9aa6f8 100644
> --- a/fs/ext4/inline.c
> +++ b/fs/ext4/inline.c
> @@ -151,6 +151,12 @@ int ext4_find_inline_data_nolock(struct inode *inode)
>  		goto out;
>  
>  	if (!is.s.not_found) {
> +		if (is.s.here->e_value_inum) {
> +			EXT4_ERROR_INODE(inode, "inline data xattr refers "
> +					 "to an external xattr inode");
> +			error = -EFSCORRUPTED;
> +			goto out;
> +		}
>  		EXT4_I(inode)->i_inline_off = (u16)((void *)is.s.here -
>  					(void *)ext4_raw_inode(&is.iloc));
>  		EXT4_I(inode)->i_inline_size = EXT4_MIN_INLINE_DATA_SIZE +
>