Messages in this thread Patch in this message | | | Subject | [PATCH][GIT PULL] tracing: Sanitize value returned from write(trace_marker, "...", len) | From | Steven Rostedt <> | Date | Fri, 13 Aug 2010 16:55:07 -0400 |
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Ingo,
I had this sitting in my quilt queue, and did not realize I never committed it. This is on top of my previous two pull requests.
Thanks,
-- Steve
Please pull the latest tip/perf/urgent-3 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git tip/perf/urgent-3
Marcin Slusarz (1): tracing: Sanitize value returned from write(trace_marker, "...", len)
---- kernel/trace/trace.c | 11 ++++++++--- 1 files changed, 8 insertions(+), 3 deletions(-) --------------------------- commit 1aa54bca6ee0d07ebcafb8ca8074b624d80724aa Author: Marcin Slusarz <marcin.slusarz@gmail.com> Date: Wed Jul 28 01:18:01 2010 +0200
tracing: Sanitize value returned from write(trace_marker, "...", len) When userspace code writes non-new-line-terminated string to trace_marker file, write handler appends new-line and returns number of bytes written to trace buffer, so write(fd, "abc", 3) will return 4 That's unexpected and unfortunately it confuses glibc's fprintf function. Example: int main() { fprintf(stderr, "abc"); return 0; } $ gcc test.c -o test $ echo mmiotrace > /sys/kernel/debug/tracing/current_tracer $ ./test 2>/sys/kernel/debug/tracing/trace_marker results in infinite loop: write(fd, "abc", 3) = 4 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 write(fd, "", 1) = 0 (...) ...and kernel trace buffer full of empty markers. Fix it by sanitizing write return value. Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com> LKML-Reference: <20100727231801.GB2826@joi.lan> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 086d363..88b42d1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3498,6 +3498,7 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, size_t cnt, loff_t *fpos) { char *buf; + size_t written; if (tracing_disabled) return -EINVAL; @@ -3519,11 +3520,15 @@ tracing_mark_write(struct file *filp, const char __user *ubuf, } else buf[cnt] = '\0'; - cnt = mark_printk("%s", buf); + written = mark_printk("%s", buf); kfree(buf); - *fpos += cnt; + *fpos += written; - return cnt; + /* don't tell userspace we wrote more - it might confuse them */ + if (written > cnt) + written = cnt; + + return written; } static int tracing_clock_show(struct seq_file *m, void *v)
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