On Thu, 2024-03-07 at 15:36 +0100, Roberto Sassu wrote:
> On Thu, 2024-03-07 at 08:31 -0600, Seth Forshee wrote:
> > 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.
>
> You are right, thank you!
(Apologies, I should have been more careful).
Roberto
> Roberto
>
> > >
> > > 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
> > >
