[PATCH v2] bpf: test_maps: Avoid possible out of bound access

[Breno Leitao <leitao@debian.org>]

When compiling test_maps selftest with GCC-8, it warns that an array might
be indexed with a negative value, which could cause a negative out of bound
access, depending on parameters of the function. This is the GCC-8 warning:

	gcc -Wall -O2 -I../../../include/uapi -I../../../lib -I../../../lib/bpf -I../../../../include/generated -DHAVE_GENHDR -I../../../include    test_maps.c /home/breno/Devel/linux/tools/testing/selftests/bpf/libbpf.a -lcap -lelf -lrt -lpthread -o /home/breno/Devel/linux/tools/testing/selftests/bpf/test_maps
	In file included from test_maps.c:16:
	test_maps.c: In function ‘run_all_tests’:
	test_maps.c:1079:10: warning: array subscript -1 is below array bounds of ‘pid_t[<Ube20> + 1]’ [-Warray-bounds]
	   assert(waitpid(pid[i], &status, 0) == pid[i]);
		  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
	test_maps.c:1059:6: warning: array subscript -1 is below array bounds of ‘pid_t[<Ube20> + 1]’ [-Warray-bounds]
	   pid[i] = fork();
	   ~~~^~~

This patch simply guarantees that the task(s) variables are unsigned, thus,
they could never be a negative number, hence avoiding an out of bound access
warning.

Signed-off-by: Breno Leitao <leitao@debian.org>
---
 tools/testing/selftests/bpf/test_maps.c | 27 +++++++++++++------------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index e2b9eee37187..6e05a22b346c 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -43,7 +43,7 @@ static int map_flags;
 	}								\
 })
 
-static void test_hashmap(int task, void *data)
+static void test_hashmap(unsigned int task, void *data)
 {
 	long long key, next_key, first_key, value;
 	int fd;
@@ -133,7 +133,7 @@ static void test_hashmap(int task, void *data)
 	close(fd);
 }
 
-static void test_hashmap_sizes(int task, void *data)
+static void test_hashmap_sizes(unsigned int task, void *data)
 {
 	int fd, i, j;
 
@@ -153,7 +153,7 @@ static void test_hashmap_sizes(int task, void *data)
 		}
 }
 
-static void test_hashmap_percpu(int task, void *data)
+static void test_hashmap_percpu(unsigned int task, void *data)
 {
 	unsigned int nr_cpus = bpf_num_possible_cpus();
 	BPF_DECLARE_PERCPU(long, value);
@@ -280,7 +280,7 @@ static int helper_fill_hashmap(int max_entries)
 	return fd;
 }
 
-static void test_hashmap_walk(int task, void *data)
+static void test_hashmap_walk(unsigned int task, void *data)
 {
 	int fd, i, max_entries = 1000;
 	long long key, value, next_key;
@@ -351,7 +351,7 @@ static void test_hashmap_zero_seed(void)
 	close(second);
 }
 
-static void test_arraymap(int task, void *data)
+static void test_arraymap(unsigned int task, void *data)
 {
 	int key, next_key, fd;
 	long long value;
@@ -406,7 +406,7 @@ static void test_arraymap(int task, void *data)
 	close(fd);
 }
 
-static void test_arraymap_percpu(int task, void *data)
+static void test_arraymap_percpu(unsigned int task, void *data)
 {
 	unsigned int nr_cpus = bpf_num_possible_cpus();
 	BPF_DECLARE_PERCPU(long, values);
@@ -502,7 +502,7 @@ static void test_arraymap_percpu_many_keys(void)
 	close(fd);
 }
 
-static void test_devmap(int task, void *data)
+static void test_devmap(unsigned int task, void *data)
 {
 	int fd;
 	__u32 key, value;
@@ -517,7 +517,7 @@ static void test_devmap(int task, void *data)
 	close(fd);
 }
 
-static void test_queuemap(int task, void *data)
+static void test_queuemap(unsigned int task, void *data)
 {
 	const int MAP_SIZE = 32;
 	__u32 vals[MAP_SIZE + MAP_SIZE/2], val;
@@ -575,7 +575,7 @@ static void test_queuemap(int task, void *data)
 	close(fd);
 }
 
-static void test_stackmap(int task, void *data)
+static void test_stackmap(unsigned int task, void *data)
 {
 	const int MAP_SIZE = 32;
 	__u32 vals[MAP_SIZE + MAP_SIZE/2], val;
@@ -641,7 +641,7 @@ static void test_stackmap(int task, void *data)
 #define SOCKMAP_PARSE_PROG "./sockmap_parse_prog.o"
 #define SOCKMAP_VERDICT_PROG "./sockmap_verdict_prog.o"
 #define SOCKMAP_TCP_MSG_PROG "./sockmap_tcp_msg_prog.o"
-static void test_sockmap(int tasks, void *data)
+static void test_sockmap(unsigned int tasks, void *data)
 {
 	struct bpf_map *bpf_map_rx, *bpf_map_tx, *bpf_map_msg, *bpf_map_break;
 	int map_fd_msg = 0, map_fd_rx = 0, map_fd_tx = 0, map_fd_break;
@@ -1258,10 +1258,11 @@ static void test_map_large(void)
 }
 
 #define run_parallel(N, FN, DATA) \
-	printf("Fork %d tasks to '" #FN "'\n", N); \
+	printf("Fork %u tasks to '" #FN "'\n", N); \
 	__run_parallel(N, FN, DATA)
 
-static void __run_parallel(int tasks, void (*fn)(int task, void *data),
+static void __run_parallel(unsigned int tasks,
+			   void (*fn)(unsigned int task, void *data),
 			   void *data)
 {
 	pid_t pid[tasks];
@@ -1302,7 +1303,7 @@ static void test_map_stress(void)
 #define DO_UPDATE 1
 #define DO_DELETE 0
 
-static void test_update_delete(int fn, void *data)
+static void test_update_delete(unsigned int fn, void *data)
 {
 	int do_update = ((int *)data)[1];
 	int fd = ((int *)data)[0];
-- 
2.19.0