[PATCH 6.4 160/800] selftests/bpf: Fix invalid pointer check in get_xlated_program()

Greg Kroah-Hartman
2023-07-16T20:00:16Z

From: Eduard Zingerman <eddyz87@gmail.com>

[ Upstream commit b23ed4d74c4d583b5f621ee4c776699442833554 ]

Dan Carpenter reported invalid check for calloc() result in
test_verifier.c:get_xlated_program():

./tools/testing/selftests/bpf/test_verifier.c:1365 get_xlated_program()
warn: variable dereferenced before check 'buf' (see line 1364)

./tools/testing/selftests/bpf/test_verifier.c
1363 *cnt = xlated_prog_len / buf_element_size;
1364 *buf = calloc(*cnt, buf_element_size);
1365 if (!buf) {

This should be if (!*buf) {

1366 perror("can't allocate xlated program buffer");
1367 return -ENOMEM;

This commit refactors the get_xlated_program() to avoid using double
pointer type.

Fixes: 933ff53191eb ("selftests/bpf: specify expected instructions in test_verifier tests")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Closes: https://lore.kernel.org/bpf/ZH7u0hEGVB4MjGZq@moroto/
Link: https://lore.kernel.org/bpf/20230609221637.2631800-1-eddyz87@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/bpf/test_verifier.c | 24 +++++++++++----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index e4657c5bc3f12..4683ff84044d6 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -1227,45 +1227,46 @@ static bool cmp_str_seq(const char *log, const char *exp)
return true;
}

-static int get_xlated_program(int fd_prog, struct bpf_insn **buf, int *cnt)
+static struct bpf_insn *get_xlated_program(int fd_prog, int *cnt)
{
+ __u32 buf_element_size = sizeof(struct bpf_insn);
struct bpf_prog_info info = {};
__u32 info_len = sizeof(info);
__u32 xlated_prog_len;
- __u32 buf_element_size = sizeof(struct bpf_insn);
+ struct bpf_insn *buf;

if (bpf_prog_get_info_by_fd(fd_prog, &info, &info_len)) {
perror("bpf_prog_get_info_by_fd failed");
- return -1;
+ return NULL;
}

xlated_prog_len = info.xlated_prog_len;
if (xlated_prog_len % buf_element_size) {
printf("Program length %d is not multiple of %d\n",
xlated_prog_len, buf_element_size);
- return -1;
+ return NULL;
}

*cnt = xlated_prog_len / buf_element_size;
- *buf = calloc(*cnt, buf_element_size);
+ buf = calloc(*cnt, buf_element_size);
if (!buf) {
perror("can't allocate xlated program buffer");
- return -ENOMEM;
+ return NULL;
}

bzero(&info, sizeof(info));
info.xlated_prog_len = xlated_prog_len;
- info.xlated_prog_insns = (__u64)(unsigned long)*buf;
+ info.xlated_prog_insns = (__u64)(unsigned long)buf;
if (bpf_prog_get_info_by_fd(fd_prog, &info, &info_len)) {
perror("second bpf_prog_get_info_by_fd failed");
goto out_free_buf;
}

- return 0;
+ return buf;

out_free_buf:
- free(*buf);
- return -1;
+ free(buf);
+ return NULL;
}

static bool is_null_insn(struct bpf_insn *insn)
@@ -1398,7 +1399,8 @@ static bool check_xlated_program(struct bpf_test *test, int fd_prog)
if (!check_expected && !check_unexpected)
goto out;

- if (get_xlated_program(fd_prog, &buf, &cnt)) {
+ buf = get_xlated_program(fd_prog, &cnt);
+ if (!buf) {
printf("FAIL: can't get xlated program\n");
result = false;
goto out;
--
2.39.2