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| author | Michal Schmidt <mschmidt@redhat.com> | 2024-05-06 17:50:22 +0300 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2024-05-06 23:42:22 +0300 |
| commit | e549b39a0ab8880d7ae6c6495b00fc1cb8f36174 (patch) | |
| tree | e2b4ed7f9f9cc6b2904155c29ccf6b4b63077b96 /tools | |
| parent | 8e6d9ae2e09f1f6ba65614a5e5c5a2a2e335dcba (diff) | |
| download | linux-e549b39a0ab8880d7ae6c6495b00fc1cb8f36174.tar.xz | |
selftests/bpf: Fix pointer arithmetic in test_xdp_do_redirect
Cast operation has a higher precedence than addition. The code here
wants to zero the 2nd half of the 64-bit metadata, but due to a pointer
arithmetic mistake, it writes the zero at offset 16 instead.
Just adding parentheses around "data + 4" would fix this, but I think
this will be slightly better readable with array syntax.
I was unable to test this with tools/testing/selftests/bpf/vmtest.sh,
because my glibc is newer than glibc in the provided VM image.
So I just checked the difference in the compiled code.
objdump -S tools/testing/selftests/bpf/xdp_do_redirect.test.o:
- *((__u32 *)data) = 0x42; /* metadata test value */
+ ((__u32 *)data)[0] = 0x42; /* metadata test value */
be7: 48 8d 85 30 fc ff ff lea -0x3d0(%rbp),%rax
bee: c7 00 42 00 00 00 movl $0x42,(%rax)
- *((__u32 *)data + 4) = 0;
+ ((__u32 *)data)[1] = 0;
bf4: 48 8d 85 30 fc ff ff lea -0x3d0(%rbp),%rax
- bfb: 48 83 c0 10 add $0x10,%rax
+ bfb: 48 83 c0 04 add $0x4,%rax
bff: c7 00 00 00 00 00 movl $0x0,(%rax)
Fixes: 5640b6d89434 ("selftests/bpf: fix "metadata marker" getting overwritten by the netstack")
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20240506145023.214248-1-mschmidt@redhat.com
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c index 498d3bdaa4b0..bad0ea167be7 100644 --- a/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c +++ b/tools/testing/selftests/bpf/prog_tests/xdp_do_redirect.c @@ -107,8 +107,8 @@ void test_xdp_do_redirect(void) .attach_point = BPF_TC_INGRESS); memcpy(&data[sizeof(__u64)], &pkt_udp, sizeof(pkt_udp)); - *((__u32 *)data) = 0x42; /* metadata test value */ - *((__u32 *)data + 4) = 0; + ((__u32 *)data)[0] = 0x42; /* metadata test value */ + ((__u32 *)data)[1] = 0; skel = test_xdp_do_redirect__open(); if (!ASSERT_OK_PTR(skel, "skel")) |