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37cce22dbd
Previously, the verifier was treating all PTR_TO_STACK registers passed to a helper call as potentially written to by the helper. However, all calls to check_stack_range_initialized() already have precise access type information available. Rather than treat ACCESS_HELPER as a proxy for BPF_WRITE, pass enum bpf_access_type to check_stack_range_initialized() to more precisely track helper arguments. One benefit from this precision is that registers tracked as valid spills and passed as a read-only helper argument remain tracked after the call. Rather than being marked STACK_MISC afterwards. An additional benefit is the verifier logs are also more precise. For this particular error, users will enjoy a slightly clearer message. See included selftest updates for examples. Acked-by: Eduard Zingerman <eddyz87@gmail.com> Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> Link: https://lore.kernel.org/r/ff885c0e5859e0cd12077c3148ff0754cad4f7ed.1736886479.git.dxu@dxuuu.xyz Signed-off-by: Alexei Starovoitov <ast@kernel.org>
20 lines
428 B
C
20 lines
428 B
C
// SPDX-License-Identifier: GPL-2.0
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#include "vmlinux.h"
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#include <bpf/bpf_helpers.h>
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#include "bpf_misc.h"
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SEC("tc/ingress")
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__description("uninit/mtu: write rejected")
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__success
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__caps_unpriv(CAP_BPF|CAP_NET_ADMIN)
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__failure_unpriv __msg_unpriv("invalid read from stack")
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int tc_uninit_mtu(struct __sk_buff *ctx)
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{
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__u32 mtu;
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bpf_check_mtu(ctx, 0, &mtu, 0, 0);
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return TCX_PASS;
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}
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char LICENSE[] SEC("license") = "GPL";
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