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Date:   Fri, 16 Feb 2018 01:00:33 -0500
From:   Richard Guy Briggs <rgb@redhat.com>
To:     Steve Grubb <sgrubb@redhat.com>
Cc:     Linux-Audit Mailing List <linux-audit@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Paul Moore <paul@paul-moore.com>,
        Eric Paris <eparis@redhat.com>
Subject: Re: [PATCH ghak8 ALT4 V4 1/3] audit: show partial pathname for
 entries with anonymous parents
Message-ID: <20180216060033.ecdwodaswxoku2ds@madcap2.tricolour.ca>
References: <cover.1518411444.git.rgb@redhat.com>
 <9a249968b7c994eaec1da8ae6d5bb48e385acf5c.1518411444.git.rgb@redhat.com>
 <2739042.dBRvusNJAk@x2>
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On 2018-02-15 18:07, Steve Grubb wrote:
> On Monday, February 12, 2018 12:02:21 AM EST Richard Guy Briggs wrote:
> > Tracefs or debugfs were causing hundreds to thousands of null PATH
> > records to be associated with the init_module and finit_module SYSCALL
> > records on a few modules when the following rule was in place for
> > startup:
> >         -a always,exit -F arch=x86_64 -S init_module -F key=mod-load
> > 
> > This happens because the parent inode is not found in the task's
> > audit_names list and hence treats it as anonymous.  This gives us no
> > information other than a numerical device number for a device that may
> > no longer be visible upon log inspeciton, and an inode number.
> > 
> > Fill in the partial known pathname from the filesystem mount point to
> > the leaf node on previously null PATH records from entries that have an
> > anonymous parent from the child dentry using dentry_path_raw().
> > 
> > Make the dentry argument of __audit_inode_child() non-const so that we
> > can take a reference to it in the case of an anonymous parent with
> > dget() and dget_parent() to be able to later print a partial path from
> > the host filesystem rather than null.
> > 
> > Since all we are given is an inode of the parent and the dentry of the
> > child, finding the path from the mount point to the root of the
> > filesystem is more challenging that would involve searching all
> > vfsmounts from "/" until a matching dentry is found for that
> > filesystem's root dentry.  Even if one is found, there may be more than
> > one mount point.  At this point the gain seems marginal since
> > knowing the filesystem type and path are a significant help in tracking
> > down the source of the PATH records and being able to address them.
> > 
> > Sample output:
> > type=PROCTITLE msg=audit(1488317694.446:143):
> > proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634 type=PATH
> > msg=audit(1488317694.446:143): item=797
> > name=events/nfs4/nfs4_setclientid/format inode=15969 dev=00:09
> > mode=0100444 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0
> > nametype=CREATE cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> > cap_fver=0 type=PATH msg=audit(1488317694.446:143): item=796
> > name=events/nfs4/nfs4_setclientid inode=15964 dev=00:09 mode=040755 ouid=0
> > ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0 nametype=PARENT
> > cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0 cap_fver=0 ...
> > type=PATH msg=audit(1488317694.446:143): item=1 name=events/nfs4
> > inode=15571 dev=00:09 mode=040755 ouid=0 ogid=0 rdev=00:00
> > obj=system_u:object_r:tracefs_t:s0 nametype=CREATE cap_fp=0000000000000000
> > cap_fi=0000000000000000 cap_fe=0 cap_fver=0 type=PATH
> > msg=audit(1488317694.446:143): item=0 name=events inode=119 dev=00:09
> > mode=040755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:tracefs_t:s0
> > nametype=PARENT cap_fp=0000000000000000 cap_fi=0000000000000000 cap_fe=0
> > cap_fver=0 type=KERN_MODULE msg=audit(1488317694.446:143): name="nfsv4"
> > type=SYSCALL msg=audit(1488317694.446:143): arch=c000003e syscall=313
> > success=yes exit=0 a0=1 a1=55d5a35ce106 a2=0 a3=1 items=798 ppid=6 pid=528
> > auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0
> > tty=(none) ses=4294967295 comm="modprobe" exe="/usr/bin/kmod"
> > subj=system_u:system_r:insmod_t:s0 key="mod-load"
> 
> Thanks for the samples, but the event above fails the ausearch-test test 
> suite. The "name" field in the PATH record is not properly escaped.

Is the ausearch-test on github yet?  Last I see is v0.6 on your rh
people page.

> -Steve
> 
> > See: https://github.com/linux-audit/audit-kernel/issues/8
> > Test case: https://github.com/linux-audit/audit-testsuite/issues/42
> > 
> > Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> > 
> > ---
> > v4:
> >   fix fullpath memleak
> >   switch from log_format() to audit_log_untrustedstring()
> >   remove leading / from pathname relative to unknown mount point
> > 
> > v3:
> >   fix audit_buffer leak and dname error allocation leak audit_log_name
> >   only put audit_name->dentry if it is being replaced
> > 
> > v2:
> >   deconstify struct dentry*
> >   add hex prefix to fstype
> > ---
> >  include/linux/audit.h |  8 ++++----
> >  kernel/audit.c        | 28 +++++++++++++++++++++++++++-
> >  kernel/audit.h        |  1 +
> >  kernel/auditsc.c      |  8 +++++++-
> >  4 files changed, 39 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > index af410d9..2020f1d 100644
> > --- a/include/linux/audit.h
> > +++ b/include/linux/audit.h
> > @@ -232,7 +232,7 @@ extern void __audit_inode(struct filename *name, const
> > struct dentry *dentry, unsigned int flags);
> >  extern void __audit_file(const struct file *);
> >  extern void __audit_inode_child(struct inode *parent,
> > -				const struct dentry *dentry,
> > +				struct dentry *dentry,
> >  				const unsigned char type);
> >  extern void __audit_seccomp(unsigned long syscall, long signr, int code);
> >  extern void __audit_ptrace(struct task_struct *t);
> > @@ -297,7 +297,7 @@ static inline void audit_inode_parent_hidden(struct
> > filename *name, AUDIT_INODE_PARENT | AUDIT_INODE_HIDDEN);
> >  }
> >  static inline void audit_inode_child(struct inode *parent,
> > -				     const struct dentry *dentry,
> > +				     struct dentry *dentry,
> >  				     const unsigned char type) {
> >  	if (unlikely(!audit_dummy_context()))
> >  		__audit_inode_child(parent, dentry, type);
> > @@ -481,7 +481,7 @@ static inline void __audit_inode(struct filename *name,
> > unsigned int flags)
> >  { }
> >  static inline void __audit_inode_child(struct inode *parent,
> > -					const struct dentry *dentry,
> > +					struct dentry *dentry,
> >  					const unsigned char type)
> >  { }
> >  static inline void audit_inode(struct filename *name,
> > @@ -495,7 +495,7 @@ static inline void audit_inode_parent_hidden(struct
> > filename *name, const struct dentry *dentry)
> >  { }
> >  static inline void audit_inode_child(struct inode *parent,
> > -				     const struct dentry *dentry,
> > +				     struct dentry *dentry,
> >  				     const unsigned char type)
> >  { }
> >  static inline void audit_core_dumps(long signr)
> > diff --git a/kernel/audit.c b/kernel/audit.c
> > index 227db99..0c8d5a8 100644
> > --- a/kernel/audit.c
> > +++ b/kernel/audit.c
> > @@ -72,6 +72,7 @@
> >  #include <linux/freezer.h>
> >  #include <linux/pid_namespace.h>
> >  #include <net/netns/generic.h>
> > +#include <linux/dcache.h>
> > 
> >  #include "audit.h"
> > 
> > @@ -2056,6 +2057,10 @@ void audit_copy_inode(struct audit_names *name,
> > const struct dentry *dentry, name->gid   = inode->i_gid;
> >  	name->rdev  = inode->i_rdev;
> >  	security_inode_getsecid(inode, &name->osid);
> > +	if (name->dentry) {
> > +		dput(name->dentry);
> > +		name->dentry = NULL;
> > +	}
> >  	audit_copy_fcaps(name, dentry);
> >  }
> > 
> > @@ -2097,8 +2102,29 @@ void audit_log_name(struct audit_context *context,
> > struct audit_names *n, audit_log_n_untrustedstring(ab, n->name->name,
> >  						    n->name_len);
> >  		}
> > -	} else
> > +	} else if (n->dentry) {
> > +		char *fullpath;
> > +		const char *fullpathp = NULL;
> > +
> > +		fullpath = kmalloc(PATH_MAX, GFP_KERNEL);
> > +		if (fullpath) {
> > +			fullpathp = dentry_path_raw(n->dentry, fullpath, PATH_MAX);
> > +			if (IS_ERR(fullpathp)) {
> > +				fullpathp = NULL;
> > +			} else {
> > +				while (*fullpathp == '/')
> > +					fullpathp++;
> > +				if (*fullpathp == 0)
> > +					fullpathp = NULL;
> > +			}
> > +		}
> > +		audit_log_format(ab, " name=");
> > +		audit_log_untrustedstring(ab, fullpathp ?: "?");
> > +		if (fullpath)
> > +			kfree(fullpath);
> > +	} else {
> >  		audit_log_format(ab, " name=(null)");
> > +	}
> > 
> >  	if (n->ino != AUDIT_INO_UNSET)
> >  		audit_log_format(ab, " inode=%lu"
> > diff --git a/kernel/audit.h b/kernel/audit.h
> > index af5bc59..81f6865 100644
> > --- a/kernel/audit.h
> > +++ b/kernel/audit.h
> > @@ -85,6 +85,7 @@ struct audit_names {
> > 
> >  	unsigned long		ino;
> >  	dev_t			dev;
> > +	struct dentry		*dentry;
> >  	umode_t			mode;
> >  	kuid_t			uid;
> >  	kgid_t			gid;
> > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > index e80459f..b73ede0 100644
> > --- a/kernel/auditsc.c
> > +++ b/kernel/auditsc.c
> > @@ -75,6 +75,7 @@
> >  #include <linux/uaccess.h>
> >  #include <linux/fsnotify_backend.h>
> >  #include <uapi/linux/limits.h>
> > +#include <linux/dcache.h>
> > 
> >  #include "audit.h"
> > 
> > @@ -882,6 +883,8 @@ static inline void audit_free_names(struct
> > audit_context *context) list_del(&n->list);
> >  		if (n->name)
> >  			putname(n->name);
> > +		if (n->dentry)
> > +			dput(n->dentry);
> >  		if (n->should_free)
> >  			kfree(n);
> >  	}
> > @@ -1862,7 +1865,7 @@ void __audit_file(const struct file *file)
> >   * unsuccessful attempts.
> >   */
> >  void __audit_inode_child(struct inode *parent,
> > -			 const struct dentry *dentry,
> > +			 struct dentry *dentry,
> >  			 const unsigned char type)
> >  {
> >  	struct audit_context *context = current->audit_context;
> > @@ -1941,6 +1944,7 @@ void __audit_inode_child(struct inode *parent,
> >  		if (!n)
> >  			return;
> >  		audit_copy_inode(n, NULL, parent);
> > +		n->dentry = dget_parent(dentry);
> >  	}
> > 
> >  	if (!found_child) {
> > @@ -1962,6 +1966,8 @@ void __audit_inode_child(struct inode *parent,
> >  		audit_copy_inode(found_child, dentry, inode);
> >  	else
> >  		found_child->ino = AUDIT_INO_UNSET;
> > +	if (!found_parent)
> > +		found_child->dentry = dget(dentry);
> >  }
> >  EXPORT_SYMBOL_GPL(__audit_inode_child);
> 
> 
> 
> 

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635