From 9efa9e499799f939968aff1123cc7e8184960e48 Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Tue, 11 Aug 2020 15:05:53 -0700 Subject: bpf, selftests: Add tests to sock_ops for loading sk Add tests to directly accesse sock_ops sk field. Then use it to ensure a bad pointer access will fault if something goes wrong. We do three tests: The first test ensures when we read sock_ops sk pointer into the same register that we don't fault as described earlier. Here r9 is chosen as the temp register. The xlated code is, 36: (7b) *(u64 *)(r1 +32) = r9 37: (61) r9 = *(u32 *)(r1 +28) 38: (15) if r9 == 0x0 goto pc+3 39: (79) r9 = *(u64 *)(r1 +32) 40: (79) r1 = *(u64 *)(r1 +0) 41: (05) goto pc+1 42: (79) r9 = *(u64 *)(r1 +32) The second test ensures the temp register selection does not collide with in-use register r9. Shown here r8 is chosen because r9 is the sock_ops pointer. The xlated code is as follows, 46: (7b) *(u64 *)(r9 +32) = r8 47: (61) r8 = *(u32 *)(r9 +28) 48: (15) if r8 == 0x0 goto pc+3 49: (79) r8 = *(u64 *)(r9 +32) 50: (79) r9 = *(u64 *)(r9 +0) 51: (05) goto pc+1 52: (79) r8 = *(u64 *)(r9 +32) And finally, ensure we didn't break the base case where dst_reg does not equal the source register, 56: (61) r2 = *(u32 *)(r1 +28) 57: (15) if r2 == 0x0 goto pc+1 58: (79) r2 = *(u64 *)(r1 +0) Notice it takes us an extra four instructions when src reg is the same as dst reg. One to save the reg, two to restore depending on the branch taken and a goto to jump over the second restore. Signed-off-by: John Fastabend Signed-off-by: Daniel Borkmann Acked-by: Song Liu Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/159718355325.4728.4163036953345999636.stgit@john-Precision-5820-Tower --- .../testing/selftests/bpf/progs/test_tcpbpf_kern.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'tools') diff --git a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c index 6420b61fbbc8..3e6912e4df3d 100644 --- a/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c +++ b/tools/testing/selftests/bpf/progs/test_tcpbpf_kern.c @@ -82,6 +82,27 @@ int bpf_testcb(struct bpf_sock_ops *skops) :: [skops] "r"(skops) : "r9", "r8"); + asm volatile ( + "r1 = %[skops];\n" + "r1 = *(u64 *)(r1 +184);\n" + "if r1 == 0 goto +1;\n" + "r1 = *(u32 *)(r1 +4);\n" + :: [skops] "r"(skops):"r1"); + + asm volatile ( + "r9 = %[skops];\n" + "r9 = *(u64 *)(r9 +184);\n" + "if r9 == 0 goto +1;\n" + "r9 = *(u32 *)(r9 +4);\n" + :: [skops] "r"(skops):"r9"); + + asm volatile ( + "r1 = %[skops];\n" + "r2 = *(u64 *)(r1 +184);\n" + "if r2 == 0 goto +1;\n" + "r2 = *(u32 *)(r2 +4);\n" + :: [skops] "r"(skops):"r1", "r2"); + op = (int) skops->op; update_event_map(op); -- cgit v1.2.3-59-g8ed1b