[tip:perf/urgent] perf: Return proper values for user stack errors

[tip-bot for Jiri Olsa]

Commit-ID:  78b562fbfa2cf0a9fcb23c3154756b690f4905c1
Gitweb:     https://git.kernel.org/tip/78b562fbfa2cf0a9fcb23c3154756b690f4905c1
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Sun, 15 Apr 2018 11:23:50 +0200
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 17 Apr 2018 09:47:39 -0300

perf: Return proper values for user stack errors

Return immediately when we find issue in the user stack checks. The
error value could get overwritten by following check for
PERF_SAMPLE_REGS_INTR.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: syzkaller-bugs@xxxxxxxxxxxxxxxx
Cc: x86@xxxxxxxxxx
Fixes: 60e2364e60e8 ("perf: Add ability to sample machine state on interrupt")
Link: http://lkml.kernel.org/r/20180415092352.12403-1-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 kernel/events/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1bae80aaabfb..67612ce359ad 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10209,9 +10209,9 @@ static int perf_copy_attr(struct perf_event_attr __user *uattr,
 		 * __u16 sample size limit.
 		 */
 		if (attr->sample_stack_user >= USHRT_MAX)
-			ret = -EINVAL;
+			return -EINVAL;
 		else if (!IS_ALIGNED(attr->sample_stack_user, sizeof(u64)))
-			ret = -EINVAL;
+			return -EINVAL;
 	}
 
 	if (!attr->sample_max_stack)