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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>
83 lines
1.8 KiB
C
83 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Converted from tools/testing/selftests/bpf/verifier/const_or.c */
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include "bpf_misc.h"
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SEC("tracepoint")
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__description("constant register |= constant should keep constant type")
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__success
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__naked void constant_should_keep_constant_type(void)
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{
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asm volatile (" \
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r1 = r10; \
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r1 += -48; \
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r2 = 34; \
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r2 |= 13; \
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r3 = 0; \
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call %[bpf_probe_read_kernel]; \
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exit; \
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" :
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: __imm(bpf_probe_read_kernel)
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: __clobber_all);
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}
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SEC("tracepoint")
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__description("constant register |= constant should not bypass stack boundary checks")
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__failure __msg("invalid write to stack R1 off=-48 size=58")
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__naked void not_bypass_stack_boundary_checks_1(void)
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{
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asm volatile (" \
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r1 = r10; \
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r1 += -48; \
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r2 = 34; \
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r2 |= 24; \
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r3 = 0; \
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call %[bpf_probe_read_kernel]; \
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exit; \
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" :
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: __imm(bpf_probe_read_kernel)
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: __clobber_all);
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}
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SEC("tracepoint")
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__description("constant register |= constant register should keep constant type")
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__success
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__naked void register_should_keep_constant_type(void)
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{
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asm volatile (" \
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r1 = r10; \
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r1 += -48; \
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r2 = 34; \
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r4 = 13; \
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r2 |= r4; \
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r3 = 0; \
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call %[bpf_probe_read_kernel]; \
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exit; \
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" :
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: __imm(bpf_probe_read_kernel)
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: __clobber_all);
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}
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SEC("tracepoint")
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__description("constant register |= constant register should not bypass stack boundary checks")
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__failure __msg("invalid write to stack R1 off=-48 size=58")
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__naked void not_bypass_stack_boundary_checks_2(void)
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{
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asm volatile (" \
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r1 = r10; \
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r1 += -48; \
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r2 = 34; \
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r4 = 24; \
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r2 |= r4; \
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r3 = 0; \
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call %[bpf_probe_read_kernel]; \
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exit; \
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" :
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: __imm(bpf_probe_read_kernel)
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: __clobber_all);
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}
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char _license[] SEC("license") = "GPL";
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