Some kernels builds might inline vfs_getattr call within fstat syscall code path, so fentry/vfs_getattr trampoline is not called.
Alexei suggested [1] we should use security_inode_getattr instead, because it's less likely to get inlined. Adding security_inode_getattr to the d_path allowed list and switching the stat trampoline to security_inode_getattr. Adding flags that indicate trampolines were called and failing the test if any of them got missed, so it's easier to identify the issue next time. [1] https://lore.kernel.org/bpf/caadnvqj0fchopqnwm+deppyij-movveg_trefyrhdabtceu...@mail.gmail.com/ Fixes: e4d1af4b16f8 ("selftests/bpf: Add test for d_path helper") Signed-off-by: Jiri Olsa <jo...@redhat.com> --- kernel/trace/bpf_trace.c | 1 + tools/testing/selftests/bpf/prog_tests/d_path.c | 6 ++++++ tools/testing/selftests/bpf/progs/test_d_path.c | 9 ++++++++- 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index b2a5380eb187..1001c053ebb3 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1122,6 +1122,7 @@ BTF_ID(func, vfs_truncate) BTF_ID(func, vfs_fallocate) BTF_ID(func, dentry_open) BTF_ID(func, vfs_getattr) +BTF_ID(func, security_inode_getattr) BTF_ID(func, filp_close) BTF_SET_END(btf_allowlist_d_path) diff --git a/tools/testing/selftests/bpf/prog_tests/d_path.c b/tools/testing/selftests/bpf/prog_tests/d_path.c index fc12e0d445ff..f507f1a6fa3a 100644 --- a/tools/testing/selftests/bpf/prog_tests/d_path.c +++ b/tools/testing/selftests/bpf/prog_tests/d_path.c @@ -120,6 +120,12 @@ void test_d_path(void) if (err < 0) goto cleanup; + if (CHECK(!bss->called_stat || !bss->called_close, + "check", + "failed to call trampolines called_stat %d, bss->called_close %d\n", + bss->called_stat, bss->called_close)) + goto cleanup; + for (int i = 0; i < MAX_FILES; i++) { CHECK(strncmp(src.paths[i], bss->paths_stat[i], MAX_PATH_LEN), "check", diff --git a/tools/testing/selftests/bpf/progs/test_d_path.c b/tools/testing/selftests/bpf/progs/test_d_path.c index 61f007855649..84e1f883f97b 100644 --- a/tools/testing/selftests/bpf/progs/test_d_path.c +++ b/tools/testing/selftests/bpf/progs/test_d_path.c @@ -15,7 +15,10 @@ char paths_close[MAX_FILES][MAX_PATH_LEN] = {}; int rets_stat[MAX_FILES] = {}; int rets_close[MAX_FILES] = {}; -SEC("fentry/vfs_getattr") +int called_stat = 0; +int called_close = 0; + +SEC("fentry/security_inode_getattr") int BPF_PROG(prog_stat, struct path *path, struct kstat *stat, __u32 request_mask, unsigned int query_flags) { @@ -23,6 +26,8 @@ int BPF_PROG(prog_stat, struct path *path, struct kstat *stat, __u32 cnt = cnt_stat; int ret; + called_stat = 1; + if (pid != my_pid) return 0; @@ -42,6 +47,8 @@ int BPF_PROG(prog_close, struct file *file, void *id) __u32 cnt = cnt_close; int ret; + called_close = 1; + if (pid != my_pid) return 0; -- 2.26.2
