Re: [PATCH] integrity: get comm using lock to avoid race in string printing

From: Mimi Zohar
Date: Wed Apr 02 2014 - 13:40:26 EST


On Wed, 2014-04-02 at 12:19 -0400, Richard Guy Briggs wrote:
> When task->comm is passed directly to audit_log_untrustedstring() without
> getting a copy or using the task_lock, there is a race that could happen that
> would output a NULL (\0) in the output string that would effectively truncate
> the rest of the report text after the comm= field in the audit, losing fields.
>
> Use get_task_comm() to get a copy while acquiring the task_lock to prevent
> this and to prevent the result from being a mixture of old and new values of
> comm.
>
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
> security/integrity/integrity_audit.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/security/integrity/integrity_audit.c b/security/integrity/integrity_audit.c
> index 85253b5..11706a2 100644
> --- a/security/integrity/integrity_audit.c
> +++ b/security/integrity/integrity_audit.c
> @@ -33,6 +33,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
> const char *cause, int result, int audit_info)
> {
> struct audit_buffer *ab;
> + char comm[sizeof(current->comm)];
>
> if (!integrity_audit_info && audit_info == 1) /* Skip info messages */
> return;
> @@ -49,7 +50,7 @@ void integrity_audit_msg(int audit_msgno, struct inode *inode,
> audit_log_format(ab, " cause=");
> audit_log_string(ab, cause);
> audit_log_format(ab, " comm=");
> - audit_log_untrustedstring(ab, current->comm);
> + audit_log_untrustedstring(ab, get_task_comm(comm, current));
> if (fname) {
> audit_log_format(ab, " name=");
> audit_log_untrustedstring(ab, fname);

This change is already being upstreamed as commit 73a6b44 "Integrity:
Pass commname via get_task_comm()".

thanks,

Mimi

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