On Thu, Mar 07, 2024 at 01:22:39PM +0100, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
>
> Use __vfs_getxattr() instead of vfs_getxattr(), in preparation for
> deprecating using the vfs_ interfaces for retrieving fscaps.
>
> __vfs_getxattr() is only used for debugging purposes, to check if kernel
> space and user space see the same xattr value.
__vfs_getxattr() won't give you the value as seen by userspace though.
Userspace goes through vfs_getxattr() -> xattr_getsecurity() ->
cap_inode_getsecurity(), which does the conversion to the value
userspace sees. __vfs_getxattr() just gives the raw disk data.
I'm also currently working on changes to my fscaps series that will make
it so that __vfs_getxattr() also cannot be used to read fscaps xattrs.
I'll fix this and other code in EVM which will be broken by that change
as part of the next version too.
>
> Cc: stable@xxxxxxxxxxxxxxx # 5.14.x
> Cc: linux-fsdevel@xxxxxxxxxxxxxxx
> Cc: Christian Brauner <brauner@xxxxxxxxxx>
> Cc: Seth Forshee (DigitalOcean) <sforshee@xxxxxxxxxx>
> Fixes: 907a399de7b0 ("evm: Check xattr size discrepancy between kernel and user")
> Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> ---
> security/integrity/evm/evm_crypto.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> index b1ffd4cc0b44..168d98c63513 100644
> --- a/security/integrity/evm/evm_crypto.c
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -278,8 +278,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
> if (size < 0)
> continue;
>
> - user_space_size = vfs_getxattr(&nop_mnt_idmap, dentry,
> - xattr->name, NULL, 0);
> + user_space_size = __vfs_getxattr(dentry, inode, xattr->name,
> + NULL, 0);
> if (user_space_size != size)
> pr_debug("file %s: xattr %s size mismatch (kernel: %d, user: %d)\n",
> dentry->d_name.name, xattr->name, size,
> --
> 2.34.1
>
