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

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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: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Alexei Starovoitov 2021-12-15 12:35:34 -08:00 committed by Daniel Borkmann
parent 588a25e924
commit 7edc3fcbf9
2 changed files with 32 additions and 0 deletions
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20
tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c
View File

@ -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.

12
tools/testing/selftests/bpf/progs/test_module_attach.c
View File

@ -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")