tracing: Have traceprobe_probes_write() not access userspace unnecessarily
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>
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@ -647,7 +647,7 @@ ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
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size_t count, loff_t *ppos,
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int (*createfn)(int, char **))
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{
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char *kbuf, *tmp;
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char *kbuf, *buf, *tmp;
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int ret = 0;
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size_t done = 0;
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size_t size;
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@ -667,27 +667,37 @@ ssize_t traceprobe_probes_write(struct file *file, const char __user *buffer,
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goto out;
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}
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kbuf[size] = '\0';
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tmp = strchr(kbuf, '\n');
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buf = kbuf;
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do {
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tmp = strchr(buf, '\n');
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if (tmp) {
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*tmp = '\0';
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size = tmp - kbuf + 1;
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} else if (done + size < count) {
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size = tmp - buf + 1;
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} else {
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size = strlen(buf);
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if (done + size < count) {
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if (buf != kbuf)
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break;
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pr_warn("Line length is too long: Should be less than %d\n",
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WRITE_BUFSIZE);
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ret = -EINVAL;
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goto out;
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}
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}
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done += size;
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/* Remove comments */
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tmp = strchr(kbuf, '#');
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tmp = strchr(buf, '#');
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if (tmp)
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*tmp = '\0';
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ret = traceprobe_command(kbuf, createfn);
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ret = traceprobe_command(buf, createfn);
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if (ret)
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goto out;
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buf += size;
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} while (done < count);
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}
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ret = done;
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