perf: Return proper values for user stack errors

commit 78b562fbfa2cf0a9fcb23c3154756b690f4905c1 upstream.

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@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: syzkaller-bugs@googlegroups.com
Cc: x86@kernel.org
Fixes: 60e2364e60e8 ("perf: Add ability to sample machine state on interrupt")
Link: http://lkml.kernel.org/r/20180415092352.12403-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 74710fad35d555f60e90ddeba4597bd69cca74bb..b1d6b9888fbaa8487e805ee1fb51d7774f2aa2c1 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9456,9 +9456,9 @@ 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_type & PERF_SAMPLE_REGS_INTR)