tracing: Have traceprobe_probes_write() not access userspace unnecessarily (1f9b3546) · Commits · 戴 / test

The code in traceprobe_probes_write() reads up to 4096 bytes from userpace for each line. If userspace passes in several lines to execute, the code will do a large read for each line, even though, it is highly likely that the first read from userspace received all of the lines at once. I changed the logic to do a single read from userspace, and to only read from userspace again if not all of the read from userspace made it in. I tested this by adding printk()s and writing files that would test -1, ==, and +1 the buffer size, to make sure that there's no overflows and that if a single line is written with +1 the buffer size, that it fails properly. Link: http://lkml.kernel.org/r/20170209180458.5c829ab2@gandalf.local.home Acked-by:

Masami Hiramatsu <mhiramat@kernel.org> Acked-by:

Namhyung Kim <namhyung@kernel.org> Signed-off-by:

Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_probe.c

+29 −19

Original line number	Diff line number	Diff line
		@@ -647,7 +647,7 @@ ssize_t traceprobe_probes_write(struct file file, const char __user buffer,
		size_t count, loff_t *ppos,
		int (createfn)(int, char *))
		{
		char kbuf, tmp;
		char kbuf, buf, *tmp;
		int ret = 0;
		size_t done = 0;
		size_t size;
		@@ -667,27 +667,37 @@ ssize_t traceprobe_probes_write(struct file file, const char __user buffer,
		goto out;
		}
		kbuf[size] = '\0';
		tmp = strchr(kbuf, '\n');

		buf = kbuf;
		do {
		tmp = strchr(buf, '\n');
		if (tmp) {
		*tmp = '\0';
		size = tmp - kbuf + 1;
		} else if (done + size < count) {
		size = tmp - buf + 1;
		} else {
		size = strlen(buf);
		if (done + size < count) {
		if (buf != kbuf)
		break;
		pr_warn("Line length is too long: Should be less than %d\n",
		WRITE_BUFSIZE);
		ret = -EINVAL;
		goto out;
		}
		}
		done += size;

		/* Remove comments */
		tmp = strchr(kbuf, '#');
		tmp = strchr(buf, '#');

		if (tmp)
		*tmp = '\0';

		ret = traceprobe_command(kbuf, createfn);
		ret = traceprobe_command(buf, createfn);
		if (ret)
		goto out;
		buf += size;

		} while (done < count);
		}
		ret = done;

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