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selftests/bpf: check null propagation only neither reg is PTR_TO_BTF_ID

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[ Upstream commit cedebd74cf ]

Verify that nullness information is not porpagated in the branches
of register to register JEQ and JNE operations if one of them is
PTR_TO_BTF_ID. Implement this in C level so we can use CO-RE.

Signed-off-by: Hao Sun <sunhao.th@gmail.com>
Suggested-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20221222024414.29539-2-sunhao.th@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Hao Sun 2022-12-22 10:44:14 +08:00 committed by Greg Kroah-Hartman
parent d4a9d2944f
commit 95fc28a8e9
2 changed files with 51 additions and 0 deletions
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9
tools/testing/selftests/bpf/prog_tests/jeq_infer_not_null.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
#include "jeq_infer_not_null_fail.skel.h"
void test_jeq_infer_not_null(void)
{
RUN_TESTS(jeq_infer_not_null_fail);
}

42
tools/testing/selftests/bpf/progs/jeq_infer_not_null_fail.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
char _license[] SEC("license") = "GPL";
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1);
__type(key, u64);
__type(value, u64);
} m_hash SEC(".maps");
SEC("?raw_tp")
__failure __msg("R8 invalid mem access 'map_value_or_null")
int jeq_infer_not_null_ptr_to_btfid(void *ctx)
{
struct bpf_map *map = (struct bpf_map *)&m_hash;
struct bpf_map *inner_map = map->inner_map_meta;
u64 key = 0, ret = 0, *val;
val = bpf_map_lookup_elem(map, &key);
/* Do not mark ptr as non-null if one of them is
* PTR_TO_BTF_ID (R9), reject because of invalid
* access to map value (R8).
*
* Here, we need to inline those insns to access
* R8 directly, since compiler may use other reg
* once it figures out val==inner_map.
*/
asm volatile("r8 = %[val];\n"
"r9 = %[inner_map];\n"
"if r8 != r9 goto +1;\n"
"%[ret] = *(u64 *)(r8 +0);\n"
: [ret] "+r"(ret)
: [inner_map] "r"(inner_map), [val] "r"(val)
: "r8", "r9");
return ret;
}