On Friday, September 19, 2014 11:41:15 AM 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.
>
> Tetsuo Handa <[email protected]>
> Signed-off-by: Richard Guy Briggs <[email protected]>
The above is a bit odd ... is that a "Signed-off-by:" from Tetsuo Handa or a
"From:"?
> ---
> I've manually checked for locking issues and found none. I've also enabled
> all the kernel lock debugging options and it came up clean.
>
> security/lsm_audit.c | 5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> index 69fdf3b..4773b91 100644
> --- a/security/lsm_audit.c
> +++ b/security/lsm_audit.c
> @@ -212,6 +212,7 @@ static void dump_common_audit_data(struct audit_buffer
> *ab, struct common_audit_data *a)
> {
> struct task_struct *tsk = current;
> + char comm[sizeof(tsk->comm)];
This makes me a bit nervous for a potential race condition between allocation
and use below. How about using TASK_COMM_LEN instead?
> /*
> * To keep stack sizes in check force programers to notice if they
> @@ -221,7 +222,7 @@ static void dump_common_audit_data(struct audit_buffer
> *ab, BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
>
> audit_log_format(ab, " pid=%d comm=", task_pid_nr(tsk));
> - audit_log_untrustedstring(ab, tsk->comm);
> + audit_log_untrustedstring(ab, get_task_comm(comm, tsk));
>
> switch (a->type) {
> case LSM_AUDIT_DATA_NONE:
> @@ -282,7 +283,7 @@ static void dump_common_audit_data(struct audit_buffer
> *ab, pid_t pid = task_pid_nr(tsk);
> if (pid) {
> audit_log_format(ab, " pid=%d comm=", pid);
> - audit_log_untrustedstring(ab, tsk->comm);
> + audit_log_untrustedstring(ab,
> get_task_comm(comm, tsk));
> }
> }
> break;
--
paul moore
security and virtualization @ redhat
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