From 1f9b3546cf4c273b6d809003244d05cf0460a5e9 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 9 Feb 2017 17:53:50 -0500 Subject: [PATCH] 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 Acked-by: Namhyung Kim Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_probe.c | 48 +++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 19 deletions(-) diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 8c0553d9afd3..2a06f1fa7001 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -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 - 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; - if (tmp) { - *tmp = '\0'; - size = tmp - kbuf + 1; - } else if (done + size < count) { - 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, '#'); + /* Remove comments */ + tmp = strchr(buf, '#'); - if (tmp) - *tmp = '\0'; + if (tmp) + *tmp = '\0'; - ret = traceprobe_command(kbuf, createfn); - if (ret) - goto out; + ret = traceprobe_command(buf, createfn); + if (ret) + goto out; + buf += size; + + } while (done < count); } ret = done; -- 2.20.1