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SubjectRe: [PATCH ALT4 V3 1/2] audit: show fstype:pathname for entries with anonymous parents
On Wed, Aug 23, 2017 at 7:03 AM, Richard Guy Briggs <rgb@redhat.com> 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 that may no longer be
> visible upon log inspeciton, and an inode number.
>
> Fill in the filesystem type, filesystem magic number and full pathname
> from the filesystem mount point 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 to address them.
>
> Sample output:
> type=PROCTITLE msg=audit(1488317694.446:143): proctitle=2F7362696E2F6D6F6470726F6265002D71002D2D006E66737634
> type=PATH msg=audit(1488317694.446:143): item=797 name=tracefs(74726163):/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
> type=PATH msg=audit(1488317694.446:143): item=796 name=tracefs(74726163):/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
> ...
> type=PATH msg=audit(1488317694.446:143): item=1 name=tracefs(74726163):/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
> type=PATH msg=audit(1488317694.446:143): item=0 name=tracefs(74726163):/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
> type=UNKNOWN[1330] 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"
>
> 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>
>
> ---
> v3:
> fix audit_buffer leak and dname error allocation leak audit_log_name
> only put audit_name->dentry if it is being replaced
>
> v2:
> minor cosmetic changes and support fs filter patch
> ---
> include/linux/audit.h | 8 ++++----
> kernel/audit.c | 19 +++++++++++++++++++
> kernel/audit.h | 1 +
> kernel/auditsc.c | 8 +++++++-
> 4 files changed, 31 insertions(+), 5 deletions(-)

...

> diff --git a/kernel/audit.c b/kernel/audit.c
> index 59e60e0..d6e6e4e 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"
>
> @@ -2047,6 +2048,10 @@ 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);
> }
>
> @@ -2088,6 +2093,20 @@ void audit_log_name(struct audit_context *context, struct audit_names *n,
> audit_log_n_untrustedstring(ab, n->name->name,
> n->name_len);
> }
> + } 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;
> + kfree(fullpath);
> + }
> + audit_log_format(ab, " name=%s(0x%lx):%s",
> + n->dentry->d_sb->s_type->name ?: "?",
> + n->dentry->d_sb->s_magic, fullpathp ?: "?");
> } else
> audit_log_format(ab, " name=(null)");

While looking this over one more time before merging I realized that
you are missing the curly braces in the "if (fullpath)" if-statement
above. This is an easy fix, and appears to be the Right Thing, so I'm
just going to fix up the patch while merging; take a look at the
result in the audit/next tree and if you have any objections let me
know so I can back it out.

I'm also only merging this patch right now, patch 2/2 needs to wait
until the corresponding userspace is ready so we can test/verify it.

--
paul moore
www.paul-moore.com

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