Re: [PATCHv2 bpf 0/2] bpf: Fix prog_array_map_poke_run map poke update

[Jiri Olsa <olsajiri@gmail.com>]

On Wed, Nov 29, 2023 at 02:23:04PM +0100, Jiri Olsa wrote:
> On Tue, Nov 28, 2023 at 11:44:33PM +0100, Ilya Leoshkevich wrote:
> > On Tue, 2023-11-28 at 10:28 +0100, Jiri Olsa wrote:
> > > hi,
> > > this patchset fixes the issue reported in [0].
> > > 
> > > For the actual fix in patch 2 I'm changing bpf_arch_text_poke to
> > > allow to skip
> > > ip address check in patch 1. I considered adding separate function
> > > for that,
> > > but because each arch implementation is bit different, adding extra
> > > arg seemed
> > > like better option.
> > > 
> > > v2 changes:
> > >   - make it work for other archs
> > > 
> > > thanks,
> > > jirka
> > > 
> > > 
> > > [0] https://syzkaller.appspot.com/bug?extid=97a4fe20470e9bc30810
> > > ---
> > > Jiri Olsa (2):
> > >       bpf: Add checkip argument to bpf_arch_text_poke
> > >       bpf, x64: Fix prog_array_map_poke_run map poke update
> > > 
> > >  arch/arm64/net/bpf_jit_comp.c   |  3 ++-
> > >  arch/riscv/net/bpf_jit_comp64.c |  5 +++--
> > >  arch/s390/net/bpf_jit_comp.c    |  3 ++-
> > >  arch/x86/net/bpf_jit_comp.c     | 24 +++++++++++++-----------
> > >  include/linux/bpf.h             |  2 +-
> > >  kernel/bpf/arraymap.c           | 31 +++++++++++--------------------
> > >  kernel/bpf/core.c               |  2 +-
> > >  kernel/bpf/trampoline.c         | 12 ++++++------
> > >  8 files changed, 39 insertions(+), 43 deletions(-)
> > 
> > Would it be possible to add a minimized version of the reproducer as a
> > testcase?
> 
> there's reproducer I used in here:
>   https://syzkaller.appspot.com/text?tag=ReproC&x=1397180f680000
> 
> I can try, but not sure I'll be able to come up with something that
> would fit as testcase.. I'll check

the test below reproduces it for me.. the only tricky part is that
I need to repeat the loop 10 times to trigger that on my setup..
which is not terrible, but not great for a test I think

jirka


---
diff --git a/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c b/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c
new file mode 100644
index 000000000000..c18751677811
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/tailcall_poke.c
@@ -0,0 +1,77 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <unistd.h>
+#include <test_progs.h>
+#include "tailcall_poke.skel.h"
+
+#define JMP_TABLE "/sys/fs/bpf/jmp_table"
+
+static int thread_exit;
+
+static void *update(void *arg)
+{
+	__u32 zero = 0, prog1_fd, prog2_fd, map_fd;
+	struct tailcall_poke *call = arg;
+
+	map_fd = bpf_map__fd(call->maps.jmp_table);
+	prog1_fd = bpf_program__fd(call->progs.call1);
+	prog2_fd = bpf_program__fd(call->progs.call2);
+
+	while (!thread_exit) {
+		bpf_map_update_elem(map_fd, &zero, &prog1_fd, BPF_ANY);
+		bpf_map_update_elem(map_fd, &zero, &prog2_fd, BPF_ANY);
+	}
+
+	return NULL;
+}
+
+void test_tailcall_poke(void)
+{
+	struct tailcall_poke *call, *test;
+	int err, cnt = 10;
+	pthread_t thread;
+
+	unlink(JMP_TABLE);
+
+	call = tailcall_poke__open_and_load();
+	if (!ASSERT_OK_PTR(call, "tailcall_poke__open"))
+		return;
+
+	err = bpf_map__pin(call->maps.jmp_table, JMP_TABLE);
+	if (!ASSERT_OK(err, "bpf_map__pin"))
+		goto out;
+
+	err = pthread_create(&thread, NULL, update, call);
+	if (!ASSERT_OK(err, "new toggler"))
+		goto out;
+
+	while (cnt--) {
+		test = tailcall_poke__open();
+		if (!ASSERT_OK_PTR(test, "tailcall_poke__open"))
+			break;
+
+		err = bpf_map__set_pin_path(test->maps.jmp_table, JMP_TABLE);
+		if (!ASSERT_OK(err, "bpf_map__pin")) {
+			tailcall_poke__destroy(test);
+			break;
+		}
+
+		bpf_program__set_autoload(test->progs.test, true);
+		bpf_program__set_autoload(test->progs.call1, false);
+		bpf_program__set_autoload(test->progs.call2, false);
+
+		err = tailcall_poke__load(test);
+		if (!ASSERT_OK(err, "tailcall_poke__load")) {
+			tailcall_poke__destroy(test);
+			break;
+		}
+
+		tailcall_poke__destroy(test);
+	}
+
+	thread_exit = 1;
+	ASSERT_OK(pthread_join(thread, NULL), "pthread_join");
+
+out:
+	bpf_map__unpin(call->maps.jmp_table, JMP_TABLE);
+	tailcall_poke__destroy(call);
+}
diff --git a/tools/testing/selftests/bpf/progs/tailcall_poke.c b/tools/testing/selftests/bpf/progs/tailcall_poke.c
new file mode 100644
index 000000000000..d4cf63c7db01
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/tailcall_poke.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+char _license[] SEC("license") = "GPL";
+
+struct {
+        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
+        __uint(max_entries, 1);
+        __uint(key_size, sizeof(__u32));
+        __uint(value_size, sizeof(__u32));
+} jmp_table SEC(".maps");
+
+SEC("?fentry/bpf_fentry_test1")
+int BPF_PROG(test, int a)
+{
+	bpf_tail_call_static(ctx, &jmp_table, 0);
+	return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(call1, int a)
+{
+	return 0;
+}
+
+SEC("fentry/bpf_fentry_test1")
+int BPF_PROG(call2, int a)
+{
+	return 0;
+}