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selftests/bpf: Fix segmentation fault in test_progs

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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.

To fix this issue, first create 4 pages of anonymous mapping, then do all
the mmap() with MAP_FIXED.

Another issue is that when unmap the second page fails, the length
parameter to delete tmp1 mappings should be 4 * page_size.

Signed-off-by: Jianlin Lv <Jianlin.Lv@arm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200810153940.125508-1-Jianlin.Lv@arm.com
This commit is contained in:
Jianlin Lv 2020-08-10 23:39:40 +08:00 committed by Daniel Borkmann
parent 63fe3fd393
commit 0390c429db
1 changed files with 15 additions and 8 deletions
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23
tools/testing/selftests/bpf/prog_tests/mmap.c
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@ -21,7 +21,7 @@ void test_mmap(void)
const long page_size = sysconf(_SC_PAGE_SIZE);
int err, duration = 0, i, data_map_fd, data_map_id, tmp_fd, rdmap_fd;
struct bpf_map *data_map, *bss_map;
void *bss_mmaped = NULL, *map_mmaped = NULL, *tmp1, *tmp2;
void *bss_mmaped = NULL, *map_mmaped = NULL, *tmp0, *tmp1, *tmp2;
struct test_mmap__bss *bss_data;
struct bpf_map_info map_info;
__u32 map_info_sz = sizeof(map_info);
@ -183,16 +183,23 @@ void test_mmap(void)
/* check some more advanced mmap() manipulations */
/* map all but last page: pages 1-3 mapped */
tmp1 = mmap(NULL, 3 * page_size, PROT_READ, MAP_SHARED,
data_map_fd, 0);
if (CHECK(tmp1 == MAP_FAILED, "adv_mmap1", "errno %d\n", errno))
tmp0 = mmap(NULL, 4 * page_size, PROT_READ, MAP_SHARED | MAP_ANONYMOUS,
-1, 0);
if (CHECK(tmp0 == MAP_FAILED, "adv_mmap0", "errno %d\n", errno))
goto cleanup;
/* map all but last page: pages 1-3 mapped */
tmp1 = mmap(tmp0, 3 * page_size, PROT_READ, MAP_SHARED | MAP_FIXED,
data_map_fd, 0);
if (CHECK(tmp0 != tmp1, "adv_mmap1", "tmp0: %p, tmp1: %p\n", tmp0, tmp1)) {
munmap(tmp0, 4 * page_size);
goto cleanup;
}
/* 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, 4 * page_size);
goto cleanup;
}
@ -201,7 +208,7 @@ void test_mmap(void)
MAP_SHARED | MAP_FIXED, data_map_fd, 0);
if (CHECK(tmp2 == MAP_FAILED, "adv_mmap3", "errno %d\n", errno)) {
munmap(tmp1, page_size);
munmap(tmp1 + 2*page_size, page_size);
munmap(tmp1 + 2*page_size, 2 * page_size);
goto cleanup;
}
CHECK(tmp1 + page_size != tmp2, "adv_mmap4",
@ -211,7 +218,7 @@ void test_mmap(void)
tmp2 = mmap(tmp1, 4 * 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 */
munmap(tmp1, 4 * page_size); /* unmap page 1 */
goto cleanup;
}
CHECK(tmp1 != tmp2, "adv_mmap6", "tmp1: %p, tmp2: %p\n", tmp1, tmp2);