From: Mimi Zohar <zohar@linux.ibm.com>
To: Casey Schaufler <casey@schaufler-ca.com>,
Roberto Sassu <roberto.sassu@huawei.com>,
mjg59@google.com
Cc: linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 04/12] ima: Move ima_reset_appraise_flags() call to post hooks
Date: Mon, 26 Apr 2021 15:49:39 -0400 [thread overview]
Message-ID: <a69b29c5be3d523dae0febe672693601b794bee6.camel@linux.ibm.com> (raw)
In-Reply-To: <d4aba724-2935-467b-e57c-cd961112190b@schaufler-ca.com>
On Wed, 2021-04-07 at 09:17 -0700, Casey Schaufler wrote:
> > diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
> > index 565e33ff19d0..1f029e4c8d7f 100644
> > --- a/security/integrity/ima/ima_appraise.c
> > +++ b/security/integrity/ima/ima_appraise.c
> > @@ -577,21 +577,40 @@ int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name,
> > if (result == 1) {
> > if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST))
> > return -EINVAL;
> > - ima_reset_appraise_flags(d_backing_inode(dentry),
> > - xvalue->type == EVM_IMA_XATTR_DIGSIG);
> > result = 0;
> > }
> > return result;
> > }
> >
> > +void ima_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
> > + const void *xattr_value, size_t xattr_value_len)
> > +{
> > + const struct evm_ima_xattr_data *xvalue = xattr_value;
> > + int result;
> > +
> > + result = ima_protect_xattr(dentry, xattr_name, xattr_value,
> > + xattr_value_len);
> > + if (result == 1)
> > + ima_reset_appraise_flags(d_backing_inode(dentry),
> > + xvalue->type == EVM_IMA_XATTR_DIGSIG);
> > +}
> > +
>
> Now you're calling ima_protect_xattr() twice for each setxattr.
> Is that safe? Is it performant? Does it matter?
The first time the call to ima_protect_xattr() prevents the
security.ima from being inappropriately modified. The second time it
resets the cached status flags. From a performance perspective,
unnecessarily re-calcuating the file hash is worse than rechecking the
security xattr string.
Mimi
next prev parent reply other threads:[~2021-04-26 19:49 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 10:52 [PATCH v5 00/12] evm: Improve usability of portable signatures Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 01/12] evm: Execute evm_inode_init_security() only when an HMAC key is loaded Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 02/12] evm: Load EVM key in ima_load_x509() to avoid appraisal Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 03/12] evm: Refuse EVM_ALLOW_METADATA_WRITES only if an HMAC key is loaded Roberto Sassu
2021-04-30 20:28 ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 04/12] ima: Move ima_reset_appraise_flags() call to post hooks Roberto Sassu
2021-04-07 16:17 ` Casey Schaufler
2021-04-07 16:31 ` Roberto Sassu
2021-04-26 19:49 ` Mimi Zohar [this message]
2021-04-07 10:52 ` [PATCH v5 05/12] evm: Introduce evm_status_revalidate() Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 06/12] evm: Ignore INTEGRITY_NOLABEL/INTEGRITY_NOXATTRS if conditions are safe Roberto Sassu
2021-05-03 0:12 ` Mimi Zohar
2021-05-03 7:55 ` Roberto Sassu
2021-05-03 12:07 ` Mimi Zohar
2021-05-03 14:15 ` Roberto Sassu
2021-05-03 14:34 ` Mimi Zohar
2021-05-04 13:16 ` Roberto Sassu
2021-05-04 13:45 ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 07/12] evm: Allow xattr/attr operations for portable signatures Roberto Sassu
2021-05-03 0:12 ` Mimi Zohar
2021-05-04 14:28 ` Roberto Sassu
2021-05-04 14:49 ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 08/12] evm: Pass user namespace to set/remove xattr hooks Roberto Sassu
2021-04-07 12:06 ` Christian Brauner
2021-04-07 10:52 ` [PATCH v5 09/12] evm: Allow setxattr() and setattr() for unmodified metadata Roberto Sassu
2021-04-07 12:05 ` Christian Brauner
2021-04-07 15:23 ` kernel test robot
2021-04-07 18:14 ` kernel test robot
2021-04-07 19:28 ` [RESEND][PATCH " Roberto Sassu
2021-05-03 13:00 ` [PATCH " Mimi Zohar
2021-05-03 14:48 ` Roberto Sassu
2021-05-03 15:13 ` Mimi Zohar
2021-05-03 15:30 ` Roberto Sassu
2021-05-03 15:11 ` Roberto Sassu
2021-05-03 15:26 ` Mimi Zohar
2021-05-03 15:32 ` Roberto Sassu
2021-05-03 15:48 ` Mimi Zohar
2021-04-07 10:52 ` [PATCH v5 10/12] ima: Allow imasig requirement to be satisfied by EVM portable signatures Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 11/12] ima: Introduce template field evmsig and write to field sig as fallback Roberto Sassu
2021-04-07 10:52 ` [PATCH v5 12/12] ima: Don't remove security.ima if file must not be appraised Roberto Sassu
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