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Date: Mon, 9 Dec 2013 10:33:07 -0500
From: Richard Guy Briggs <rgb@...hat.com>
To: William Roberts <bill.c.roberts@...il.com>
Cc: linux-audit@...hat.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
William Roberts <wroberts@...sys.com>
Subject: Re: [PATCH 3/3] audit: Audit proc cmdline value
On Mon, Dec 02, 2013 at 01:10:39PM -0800, William Roberts wrote:
> During an audit event, cache and print the value of the process's
> cmdline value (proc/<pid>/cmdline). This is useful in situations
> where processes are started via fork'd virtual machines where the
> comm field is incorrect. Often times, setting the comm field still
> is insufficient as the comm width is not very wide and most
> virtual machine "package names" do not fit. Also, during execution,
> many threads have thier comm field set as well. By tying it back to
> the global cmdline value for the process, audit records will be more
> complete in systems with these properties. An example of where this
> is useful and applicable is in the realm of Android.
>
> The cached cmdline is tied to the lifecycle of the audit_context
> structure and is built on demand.
>
> Signed-off-by: William Roberts <wroberts@...sys.com>
Acked-by: Richard Guy Briggs <rgb@...hat.com>
I'll Signed-off-by: when I add it to my for-next tree.
> ---
> kernel/audit.h | 1 +
> kernel/auditsc.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 83 insertions(+)
>
> diff --git a/kernel/audit.h b/kernel/audit.h
> index b779642..bd6211f 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -202,6 +202,7 @@ struct audit_context {
> } execve;
> };
> int fds[2];
> + char *cmdline;
>
> #if AUDIT_DEBUG
> int put_count;
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index 90594c9..bfb1698 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -842,6 +842,14 @@ static inline struct audit_context *audit_get_context(struct task_struct *tsk,
> return context;
> }
>
> +static inline void audit_cmdline_free(struct audit_context *context)
> +{
> + if (!context->cmdline)
> + return;
> + kfree(context->cmdline);
> + context->cmdline = NULL;
> +}
> +
> static inline void audit_free_names(struct audit_context *context)
> {
> struct audit_names *n, *next;
> @@ -955,6 +963,7 @@ static inline void audit_free_context(struct audit_context *context)
> audit_free_aux(context);
> kfree(context->filterkey);
> kfree(context->sockaddr);
> + audit_cmdline_free(context);
> kfree(context);
> }
>
> @@ -1271,6 +1280,78 @@ static void show_special(struct audit_context *context, int *call_panic)
> audit_log_end(ab);
> }
>
> +static char *audit_cmdline_get(struct audit_buffer *ab,
> + struct task_struct *task)
> +{
> + int len;
> + int res;
> + char *buf;
> + struct mm_struct *mm;
> +
> + if (!ab || !task)
> + return NULL;
> +
> + mm = get_task_mm(task);
> + if (!mm)
> + return NULL;
> +
> + len = get_cmdline_length(mm);
> + if (!len)
> + goto mm_err;
> +
> + if (len > PATH_MAX)
> + len = PATH_MAX;
> +
> + buf = kmalloc(len, GFP_KERNEL);
> + if (!buf)
> + goto mm_err;
> +
> + res = copy_cmdline(task, mm, buf, len);
> + if (res <= 0)
> + goto alloc_err;
> +
> + mmput(mm);
> + /*
> + * res is guarenteed not to be longer than
> + * than the buf as it was truncated to len
> + * in copy_cmdline()
> + */
> + len = res;
> +
> + /*
> + * Ensure NULL terminated as application
> + * could be using setproctitle(3)
> + */
> + buf[len-1] = '\0';
> + return buf;
> +
> +alloc_err:
> + kfree(buf);
> +mm_err:
> + mmput(mm);
> + return NULL;
> +}
> +
> +static void audit_log_cmdline(struct audit_buffer *ab, struct task_struct *tsk,
> + struct audit_context *context)
> +{
> + char *msg = "(null)";
> + audit_log_format(ab, " cmdline=");
> +
> + /* Already cached */
> + if (context->cmdline) {
> + msg = context->cmdline;
> + goto out;
> + }
> + /* Not cached */
> + context->cmdline = audit_cmdline_get(ab, tsk);
> + if (!context->cmdline)
> + goto out;
> + msg = context->cmdline;
> +out:
> + audit_log_untrustedstring(ab, msg);
> +}
> +
> static void audit_log_exit(struct audit_context *context, struct task_struct *tsk)
> {
> int i, call_panic = 0;
> @@ -1302,6 +1383,7 @@ static void audit_log_exit(struct audit_context *context, struct task_struct *ts
> context->name_count);
>
> audit_log_task_info(ab, tsk);
> + audit_log_cmdline(ab, tsk, context);
> audit_log_key(ab, context->filterkey);
> audit_log_end(ab);
>
> --
> 1.7.9.5
>
> --
> Linux-audit mailing list
> Linux-audit@...hat.com
> https://www.redhat.com/mailman/listinfo/linux-audit
- RGB
--
Richard Guy Briggs <rbriggs@...hat.com>
Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
Remote, Ottawa, Canada
Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545
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