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Message-Id: <1514280416-29659-1-git-send-email-changbin.du@intel.com> Date: Tue, 26 Dec 2017 17:26:56 +0800 From: changbin.du@...el.com To: peterz@...radead.org, mingo@...hat.com, acme@...nel.org, alexander.shishkin@...ux.intel.com, jolsa@...hat.com Cc: linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org, Changbin Du <changbin.du@...el.com> Subject: [PATCH] perf ftrace: Fix the buffer size in __write_tracing_file From: Changbin Du <changbin.du@...el.com> The terminal character '\0' should take into account as size of the string buffer. Without this fix, the '--graph-funcs', '--nograph-funcs' and '--trace-funcs' options didn't work as expected when the <func> doesn't exist. I didn't dive into kernel ftrace fops, but strace shows that if usersapce writes a non-terminated string, the kernel side will return success but no filter applied. After this fix in userspace, the kernel will return an error. $ sudo ./perf ftrace -a --graph-depth 1 --graph-funcs abcdefg 0) 0.140 us | rcu_all_qs(); 3) 0.304 us | mutex_unlock(); 0) 0.153 us | find_vma(); 3) 0.088 us | __fsnotify_parent(); 0) 6.145 us | handle_mm_fault(); 3) 0.089 us | fsnotify(); 3) 0.161 us | __sb_end_write(); 3) 0.710 us | SyS_close(); 3) 7.848 us | exit_to_usermode_loop(); On above example, I specified function filter 'abcdefg' but all functions are enabled. Signed-off-by: Changbin Du <changbin.du@...el.com> --- tools/perf/builtin-ftrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/builtin-ftrace.c b/tools/perf/builtin-ftrace.c index 25a42ac..2604a64 100644 --- a/tools/perf/builtin-ftrace.c +++ b/tools/perf/builtin-ftrace.c @@ -69,7 +69,7 @@ static int __write_tracing_file(const char *name, const char *val, bool append) { char *file; int fd, ret = -1; - ssize_t size = strlen(val); + ssize_t size = strlen(val) + 1; int flags = O_WRONLY; char errbuf[512]; -- 2.7.4
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