6.5-stable review patch. If anyone has any objections, please let me know.
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From: Jinghao Jia jinghao@linux.ibm.com
[ Upstream commit 9220c3ef6fefbf18f24aeedb1142a642b3de0596 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- samples/bpf/syscall_tp_user.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/samples/bpf/syscall_tp_user.c b/samples/bpf/syscall_tp_user.c index 18c94c7e8a40e..7a09ac74fac07 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]);