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selftests/bpf: Validate frozen map contents stays frozen 

Test that frozen and mmap()'ed BPF map can't be mprotect()'ed as writable or
executable memory. Also validate that "downgrading" from writable to read-only
doesn't screw up internal writable count accounting for the purposes of map
freezing.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200410202613.3679837-2-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-04-10 13:26:13 -07:00 committed by Daniel Borkmann
parent 1f6cb19be2
commit 642c165470
1 changed files with 60 additions and 2 deletions
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62
tools/testing/selftests/bpf/prog_tests/mmap.c
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@ -19,15 +19,16 @@ void test_mmap(void)
const size_t map_sz = roundup_page(sizeof(struct map_data));
const int zero = 0, one = 1, two = 2, far = 1500;
const long page_size = sysconf(_SC_PAGE_SIZE);
int err, duration = 0, i, data_map_fd;
int err, duration = 0, i, data_map_fd, data_map_id, tmp_fd;
struct bpf_map *data_map, *bss_map;
void *bss_mmaped = NULL, *map_mmaped = NULL, *tmp1, *tmp2;
struct test_mmap__bss *bss_data;
struct bpf_map_info map_info;
__u32 map_info_sz = sizeof(map_info);
struct map_data *map_data;
struct test_mmap *skel;
__u64 val = 0;
skel = test_mmap__open_and_load();
if (CHECK(!skel, "skel_open_and_load", "skeleton open/load failed\n"))
return;
@ -36,6 +37,14 @@ void test_mmap(void)
data_map = skel->maps.data_map;
data_map_fd = bpf_map__fd(data_map);
/* get map's ID */
memset(&map_info, 0, map_info_sz);
err = bpf_obj_get_info_by_fd(data_map_fd, &map_info, &map_info_sz);
if (CHECK(err, "map_get_info", "failed %d\n", errno))
goto cleanup;
data_map_id = map_info.id;
/* mmap BSS map */
bss_mmaped = mmap(NULL, bss_sz, PROT_READ | PROT_WRITE, MAP_SHARED,
bpf_map__fd(bss_map), 0);
if (CHECK(bss_mmaped == MAP_FAILED, "bss_mmap",
@ -98,6 +107,10 @@ void test_mmap(void)
"data_map freeze succeeded: err=%d, errno=%d\n", err, errno))
goto cleanup;
err = mprotect(map_mmaped, map_sz, PROT_READ);
if (CHECK(err, "mprotect_ro", "mprotect to r/o failed %d\n", errno))
goto cleanup;
/* unmap R/W mapping */
err = munmap(map_mmaped, map_sz);
map_mmaped = NULL;
@ -111,6 +124,12 @@ void test_mmap(void)
map_mmaped = NULL;
goto cleanup;
}
err = mprotect(map_mmaped, map_sz, PROT_WRITE);
if (CHECK(!err, "mprotect_wr", "mprotect() succeeded unexpectedly!\n"))
goto cleanup;
err = mprotect(map_mmaped, map_sz, PROT_EXEC);
if (CHECK(!err, "mprotect_ex", "mprotect() succeeded unexpectedly!\n"))
goto cleanup;
map_data = map_mmaped;
/* map/unmap in a loop to test ref counting */
@ -197,6 +216,45 @@ void test_mmap(void)
CHECK_FAIL(map_data->val[far] != 3 * 321);
munmap(tmp2, 4 * page_size);
tmp1 = mmap(NULL, map_sz, PROT_READ, MAP_SHARED, data_map_fd, 0);
if (CHECK(tmp1 == MAP_FAILED, "last_mmap", "failed %d\n", errno))
goto cleanup;
test_mmap__destroy(skel);
skel = NULL;
CHECK_FAIL(munmap(bss_mmaped, bss_sz));
bss_mmaped = NULL;
CHECK_FAIL(munmap(map_mmaped, map_sz));
map_mmaped = NULL;
/* map should be still held by active mmap */
tmp_fd = bpf_map_get_fd_by_id(data_map_id);
if (CHECK(tmp_fd < 0, "get_map_by_id", "failed %d\n", errno)) {
munmap(tmp1, map_sz);
goto cleanup;
}
close(tmp_fd);
/* this should release data map finally */
munmap(tmp1, map_sz);
/* we need to wait for RCU grace period */
for (i = 0; i < 10000; i++) {
__u32 id = data_map_id - 1;
if (bpf_map_get_next_id(id, &id) || id > data_map_id)
break;
usleep(1);
}
/* should fail to get map FD by non-existing ID */
tmp_fd = bpf_map_get_fd_by_id(data_map_id);
if (CHECK(tmp_fd >= 0, "get_map_by_id_after",
"unexpectedly succeeded %d\n", tmp_fd)) {
close(tmp_fd);
goto cleanup;
}
cleanup:
if (bss_mmaped)
CHECK_FAIL(munmap(bss_mmaped, bss_sz));