[PATCH bpf-next] bpf: fix segmentation fault of test_progs

[Jianlin Lv]

test_progs reports the segmentation fault as below

$ sudo ./test_progs -t mmap --verbose
test_mmap:PASS:skel_open_and_load 0 nsec
......
test_mmap:PASS:adv_mmap1 0 nsec
test_mmap:PASS:adv_mmap2 0 nsec
test_mmap:PASS:adv_mmap3 0 nsec
test_mmap:PASS:adv_mmap4 0 nsec
Segmentation fault

This issue was triggered because mmap() and munmap() used inconsistent
length parameters; mmap() creates a new mapping of 3*page_size, but the
length parameter set in the subsequent re-map and munmap() functions is
4*page_size; this leads to the destruction of the process space.

Another issue is that when unmap the second page fails, the length
parameter to delete tmp1 mappings should be 3*page_size.

Signed-off-by: Jianlin Lv <jianlin...@arm.com>
---
 tools/testing/selftests/bpf/prog_tests/mmap.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/mmap.c 
b/tools/testing/selftests/bpf/prog_tests/mmap.c
index 43d0b5578f46..2070cfe19cac 100644
--- a/tools/testing/selftests/bpf/prog_tests/mmap.c
+++ b/tools/testing/selftests/bpf/prog_tests/mmap.c
@@ -192,7 +192,7 @@ void test_mmap(void)
        /* unmap second page: pages 1, 3 mapped */
        err = munmap(tmp1 + page_size, page_size);
        if (CHECK(err, "adv_mmap2", "errno %d\n", errno)) {
-               munmap(tmp1, map_sz);
+               munmap(tmp1, 3 * page_size);
                goto cleanup;
        }
 
@@ -207,8 +207,8 @@ void test_mmap(void)
        CHECK(tmp1 + page_size != tmp2, "adv_mmap4",
              "tmp1: %p, tmp2: %p\n", tmp1, tmp2);
 
-       /* re-map all 4 pages */
-       tmp2 = mmap(tmp1, 4 * page_size, PROT_READ, MAP_SHARED | MAP_FIXED,
+       /* re-map all 3 pages */
+       tmp2 = mmap(tmp1, 3 * page_size, PROT_READ, MAP_SHARED | MAP_FIXED,
                    data_map_fd, 0);
        if (CHECK(tmp2 == MAP_FAILED, "adv_mmap5", "errno %d\n", errno)) {
                munmap(tmp1, 3 * page_size); /* unmap page 1 */
@@ -226,7 +226,7 @@ void test_mmap(void)
        CHECK_FAIL(map_data->val[2] != 321);
        CHECK_FAIL(map_data->val[far] != 3 * 321);
 
-       munmap(tmp2, 4 * page_size);
+       munmap(tmp2, 3 * page_size);
 
        /* map all 4 pages, but with pg_off=1 page, should fail */
        tmp1 = mmap(NULL, 4 * page_size, PROT_READ, MAP_SHARED | MAP_FIXED,
-- 
2.17.1