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3ce6b42458
Add verifier tests covering pointer arithmetic on a PTR_TO_FLOW_KEYS register. This covers the bpf-next regression where an out-of-bounds constant offset introduced as flow_keys += K and then dereferenced at insn->off 0 was accepted, while the equivalent flow_keys + K direct offset was rejected. The tests check that in-bounds constant arithmetic on the keys pointer is still accepted, out-of-bounds constant arithmetic is rejected for both read and write, and a truly varying offset from bpf_get_prandom_u32() remains rejected by the existing PTR_TO_FLOW_KEYS pointer arithmetic rules. Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn> Acked-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20260606-c3-01-v3-v3-2-97c51f592f15@mails.tsinghua.edu.cn Signed-off-by: Alexei Starovoitov <ast@kernel.org>
98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Bounds checks for PTR_TO_FLOW_KEYS pointer arithmetic. */
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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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/* sizeof(struct bpf_flow_keys) is well under 4096, so +0x1000 is OOB. */
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SEC("flow_dissector")
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__description("flow_keys: in-bounds constant pointer arithmetic accepted")
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__success
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__naked void flow_keys_const_inbounds(void)
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{
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asm volatile (" \
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r1 = *(u64 *)(r1 + %[flow_keys]); \
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r1 += 8; \
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r0 = *(u64 *)(r1 + 0); \
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r0 = 0; \
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exit; \
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" :
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: __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys))
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: __clobber_all);
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}
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SEC("flow_dissector")
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__description("flow_keys: OOB via constant pointer arithmetic rejected")
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__failure __msg("invalid access to flow keys off=4096 size=8")
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__naked void flow_keys_const_oob_read(void)
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{
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asm volatile (" \
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r1 = *(u64 *)(r1 + %[flow_keys]); \
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r1 += 4096; \
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r0 = *(u64 *)(r1 + 0); \
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r0 = 0; \
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exit; \
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" :
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: __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys))
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: __clobber_all);
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}
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SEC("flow_dissector")
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__description("flow_keys: OOB write via constant pointer arithmetic rejected")
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__failure __msg("invalid access to flow keys off=4096 size=8")
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__naked void flow_keys_const_oob_write(void)
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{
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asm volatile (" \
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r1 = *(u64 *)(r1 + %[flow_keys]); \
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r1 += 4096; \
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r2 = 0; \
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*(u64 *)(r1 + 0) = r2; \
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r0 = 0; \
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exit; \
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" :
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: __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys))
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: __clobber_all);
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}
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/* Equivalent OOB expressed directly in insn->off; this form was always
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* rejected and is kept to show both forms now share one diagnostic.
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*/
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SEC("flow_dissector")
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__description("flow_keys: OOB via insn->off rejected")
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__failure __msg("invalid access to flow keys off=4096 size=8")
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__naked void flow_keys_insn_off_oob(void)
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{
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asm volatile (" \
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r1 = *(u64 *)(r1 + %[flow_keys]); \
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r0 = *(u64 *)(r1 + 4096); \
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r0 = 0; \
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exit; \
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" :
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: __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys))
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: __clobber_all);
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}
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SEC("flow_dissector")
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__description("flow_keys: variable pointer arithmetic rejected")
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__failure __msg("R1 pointer arithmetic on flow_keys prohibited")
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__naked void flow_keys_var_read(void)
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{
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asm volatile (" \
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r6 = r1; \
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call %[bpf_get_prandom_u32]; \
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r0 &= 0xFFFF; \
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r1 = *(u64 *)(r6 + %[flow_keys]); \
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r1 += r0; \
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r0 = *(u64 *)(r1 + 0); \
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r0 = 0; \
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exit; \
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" :
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: __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)),
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__imm(bpf_get_prandom_u32)
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: __clobber_all);
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}
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char _license[] SEC("license") = "GPL";
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