3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiri Olsa <jo...@kernel.org>

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 <jo...@kernel.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Andi Kleen <a...@firstfloor.org>
Cc: H. Peter Anvin <h...@zytor.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephane Eranian <eran...@google.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: syzkaller-b...@googlegroups.com
Cc: x...@kernel.org
Fixes: 60e2364e60e8 ("perf: Add ability to sample machine state on interrupt")
Link: http://lkml.kernel.org/r/20180415092352.12403-1-jo...@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <a...@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 kernel/events/core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7348,9 +7348,9 @@ static int perf_copy_attr(struct perf_ev
                 * __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;
        }
 
 out:


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