Commit 7edc3fcb authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

selftest/bpf: Add a test that reads various addresses. 



Add a function to bpf_testmod that returns invalid kernel and user addresses.
Then attach an fexit program to that function that tries to read
memory through these addresses.

This logic checks that bpf_probe_read_kernel and BPF_PROBE_MEM logic is sane.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 588a25e9

tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c

+20 −0
Original line number Diff line number Diff line
@@ -33,6 +33,22 @@ noinline int bpf_testmod_loop_test(int n) 
	return sum;

}



__weak noinline struct file *bpf_testmod_return_ptr(int arg)

{

	static struct file f = {};



	switch (arg) {

	case 1: return (void *)EINVAL;		/* user addr */

	case 2: return (void *)0xcafe4a11;	/* user addr */

	case 3: return (void *)-EINVAL;		/* canonical, but invalid */

	case 4: return (void *)(1ull << 60);	/* non-canonical and invalid */

	case 5: return (void *)~(1ull << 30);	/* trigger extable */

	case 6: return &f;			/* valid addr */

	case 7: return (void *)((long)&f | 1);	/* kernel tricks */

	default: return NULL;

	}

}



noinline ssize_t

bpf_testmod_test_read(struct file *file, struct kobject *kobj,

		      struct bin_attribute *bin_attr,
@@ -43,6 +59,10 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, 
		.off = off,

		.len = len,

	};

	int i = 1;



	while (bpf_testmod_return_ptr(i))

		i++;



	/* This is always true. Use the check to make sure the compiler

	 * doesn't remove bpf_testmod_loop_test.

tools/testing/selftests/bpf/progs/test_module_attach.c

+12 −0
Original line number Diff line number Diff line
@@ -87,6 +87,18 @@ int BPF_PROG(handle_fexit, 
	return 0;

}



SEC("fexit/bpf_testmod_return_ptr")

int BPF_PROG(handle_fexit_ret, int arg, struct file *ret)

{

	long buf = 0;



	bpf_probe_read_kernel(&buf, 8, ret);

	bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);

	*(volatile long long *)ret;

	*(volatile int *)&ret->f_mode;

	return 0;

}



__u32 fmod_ret_read_sz = 0;



SEC("fmod_ret/bpf_testmod_test_read")