[tip: core/rcu] refperf: Avoid null pointer dereference when buf fails to allocate

[tip-bot2 for Colin Ian King]

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     58db5785b0d76be4582a32a7900acce88e691d36
Gitweb:        https://git.kernel.org/tip/58db5785b0d76be4582a32a7900acce88e691d36
Author:        Colin Ian King <colin.king@xxxxxxxxxxxxx>
AuthorDate:    Thu, 16 Jul 2020 15:38:56 +01:00
Committer:     Paul E. McKenney <paulmck@xxxxxxxxxx>
CommitterDate: Mon, 24 Aug 2020 18:45:35 -07:00

refperf: Avoid null pointer dereference when buf fails to allocate

Currently in the unlikely event that buf fails to be allocated it
is dereferenced a few times.  Use the errexit flag to determine if
buf should be written to to avoid the null pointer dereferences.

Addresses-Coverity: ("Dereference after null check")
Fixes: f518f154ecef ("refperf: Dynamically allocate experiment-summary output buffer")
Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
 kernel/rcu/refscale.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index d9291f8..952595c 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -546,9 +546,11 @@ static int main_func(void *arg)
 	// Print the average of all experiments
 	SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");
 
-	buf[0] = 0;
-	strcat(buf, "\n");
-	strcat(buf, "Runs\tTime(ns)\n");
+	if (!errexit) {
+		buf[0] = 0;
+		strcat(buf, "\n");
+		strcat(buf, "Runs\tTime(ns)\n");
+	}
 
 	for (exp = 0; exp < nruns; exp++) {
 		u64 avg;