Re: [PATCH] Audit of POSIX Message Queue Syscalls v.2

[Linda Knippers <linda.knippers@hp.com>]

Hi George,

> 	> memory leak from above allocation.
> 	These do not appear to be leaks.  They always get freed in
> 	do_syscall_trace_leave(), both when the syscalls return -EFAULT and
> 	when audit is disabled.  I verified this with printk's.  With the
> 	check for audit enabled, they no longer get allocated needlessly.
> 	Unless a syscall can bypass do_syscall_trace_leave(), these look
> 	like they don't leak.

I think you do have some memory leaks.  For example:

> +int audit_mq_open(int oflag, mode_t mode, struct mq_attr __user *u_attr)
> +{
> +	struct audit_aux_data_mq_open *ax;
> +	struct audit_context *context = current->audit_context;
> +
> +	if (!audit_enabled)
> +		return 0;
> +
> +	if (likely(!context))
> +		return 0;
> +
> +	ax = kmalloc(sizeof(*ax), GFP_ATOMIC);
> +	if (!ax)
> +		return -ENOMEM;
> +
> +	if (u_attr != NULL) {
> +		if (copy_from_user(&ax->attr, u_attr, sizeof(ax->attr)))
> +			return -EFAULT;

If this return is taken, the memory allocated above will not be freed
at syscall exit time because the assignment of context->aux was not
made.  ax needs to be freed before returning from the error paths.

> +	} else
> +		memset(&ax->attr, 0, sizeof(ax->attr));
> +
> +	ax->oflag = oflag;
> +	ax->mode = mode;
> +
> +	ax->d.type = AUDIT_MQ_OPEN;
> +	ax->d.next = context->aux;
> +	context->aux = (void *)ax;
> +	return 0;
> +}

There are similar cases in other functions.

-- ljk