[PATCH bpf-next] bpf: fix segmentation fault of test_progs
From: Jianlin Lv <hidden>
Date: 2020-08-07 17:20:38
Also in:
bpf, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
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 <redacted> --- 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