linux-kernel - [PATCH] perf bench numa: Fix for loop in do

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Date:   Thu, 30 Mar 2023 09:42:02 +0200
From:   Andreas Herrmann <aherrmann@...e.de>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        Andreas Herrmann <aherrmann@...e.de>
Subject: [PATCH] perf bench numa: Fix for loop in do_work

j is of type int and start/end are of type long. Thus j might become
negative and cause segfault in access_data(). Fix it by using long for
j as well.

Signed-off-by: Andreas Herrmann <aherrmann@...e.de>
---
 tools/perf/bench/numa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Example of segfault (with 6.3.0-rc4) is:

# ./perf bench numa mem -d -m -p 2 -t 12 -P 25425
...
 threads initialized in 6.052135 seconds.
 #
perf: bench/numa.c:1654: __bench_numa: Assertion `!(!(((wait_stat) & 0x7f) == 0))' failed.
Aborted (core dumped)
# dmesg | grep segfault
[78812.711311] thread 1/3[43215]: segfault at 7f07936c9ec0 ip 00000000004ab6d0 sp 00007f0acb1f9cb0 error 4
[78812.711309] thread 1/9[43221]: segfault at 7f08bda71a70 ip 00000000004ab6d0 sp 00007f0ac81f3cb0 error 4
[78812.711316] thread 1/4[43216]: segfault at 7f07ccf76a08 ip 00000000004ab6d0 sp 00007f0aca9f8cb0 error 4
[78812.711325] thread 1/2[43214]: segfault at 7f08be2f44b0 ip 00000000004ab6d0 sp 00007f0acb9facb0 error 4
[78812.711328] thread 1/8[43220]: segfault at 7f06d3096b20 ip 00000000004ab6d0 sp 00007f0ac89f4cb0 error 4
[78812.711345] thread 1/6[43218]: segfault at 7f0774b46a18 ip 00000000004ab6d0 sp 00007f0ac99f6cb0 error 4 in perf[400000+caa000] likely on CPU 6 (core 8, socket 0)
[78812.711366] thread 0/0[43224]: segfault at 7f08a936b130 ip 00000000004ab6d0 sp 00007f0acc9fccb0 error 4 in perf[400000+caa000] likely on CPU 1 (core 1, socket 0)

diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index 9717c6c17433..1fbd7c947abc 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -847,7 +847,7 @@ static u64 do_work(u8 *__data, long bytes, int nr, int nr_max, int loop, u64 val
 
 	if (g->p.data_rand_walk) {
 		u32 lfsr = nr + loop + val;
-		int j;
+		long j;
 
 		for (i = 0; i < words/1024; i++) {
 			long start, end;
-- 
2.39.1