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authorJinghao Jia <jinghao@linux.ibm.com>2023-09-17 16:42:20 -0500
committerAlexei Starovoitov <ast@kernel.org>2023-09-21 14:32:47 -0700
commit9220c3ef6fefbf18f24aeedb1142a642b3de0596 (patch)
treeac83062572f63b2577f6777d8fefd12828e4e2a9
parent0ee352fe0d28015cab161b04d202fa3231c0ba3b (diff)
samples/bpf: syscall_tp_user: Fix array out-of-bound access
Commit 06744f24696e ("samples/bpf: Add openat2() enter/exit tracepoint to syscall_tp sample") added two more eBPF programs to support the openat2() syscall. However, it did not increase the size of the array that holds the corresponding bpf_links. This leads to an out-of-bound access on that array in the bpf_object__for_each_program loop and could corrupt other variables on the stack. On our testing QEMU, it corrupts the map1_fds array and causes the sample to fail: # ./syscall_tp prog #0: map ids 4 5 verify map:4 val: 5 map_lookup failed: Bad file descriptor Dynamically allocate the array based on the number of programs reported by libbpf to prevent similar inconsistencies in the future Fixes: 06744f24696e ("samples/bpf: Add openat2() enter/exit tracepoint to syscall_tp sample") Signed-off-by: Jinghao Jia <jinghao@linux.ibm.com> Signed-off-by: Ruowen Qin <ruowenq2@illinois.edu> Signed-off-by: Jinghao Jia <jinghao7@illinois.edu> Link: https://lore.kernel.org/r/20230917214220.637721-4-jinghao7@illinois.edu Signed-off-by: Alexei Starovoitov <ast@kernel.org>
-rw-r--r--samples/bpf/syscall_tp_user.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/samples/bpf/syscall_tp_user.c b/samples/bpf/syscall_tp_user.c
index 18c94c7e8a40..7a09ac74fac0 100644
--- a/samples/bpf/syscall_tp_user.c
+++ b/samples/bpf/syscall_tp_user.c
@@ -48,7 +48,7 @@ static void verify_map(int map_id)
static int test(char *filename, int nr_tests)
{
int map0_fds[nr_tests], map1_fds[nr_tests], fd, i, j = 0;
- struct bpf_link *links[nr_tests * 4];
+ struct bpf_link **links = NULL;
struct bpf_object *objs[nr_tests];
struct bpf_program *prog;
@@ -60,6 +60,19 @@ static int test(char *filename, int nr_tests)
goto cleanup;
}
+ /* One-time initialization */
+ if (!links) {
+ int nr_progs = 0;
+
+ bpf_object__for_each_program(prog, objs[i])
+ nr_progs += 1;
+
+ links = calloc(nr_progs * nr_tests, sizeof(struct bpf_link *));
+
+ if (!links)
+ goto cleanup;
+ }
+
/* load BPF program */
if (bpf_object__load(objs[i])) {
fprintf(stderr, "loading BPF object file failed\n");
@@ -107,8 +120,12 @@ static int test(char *filename, int nr_tests)
}
cleanup:
- for (j--; j >= 0; j--)
- bpf_link__destroy(links[j]);
+ if (links) {
+ for (j--; j >= 0; j--)
+ bpf_link__destroy(links[j]);
+
+ free(links);
+ }
for (i--; i >= 0; i--)
bpf_object__close(objs[i]);