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04013c3ca0
Add selftests to verify SOCK_OPS_GET_SK() and SOCK_OPS_GET_FIELD() correctly return NULL/zero when dst_reg == src_reg and is_fullsock == 0. Three subtests are included: - get_sk: ctx->sk with same src/dst register (SOCK_OPS_GET_SK) - get_field: ctx->snd_cwnd with same src/dst register (SOCK_OPS_GET_FIELD) - get_sk_diff_reg: ctx->sk with different src/dst register (baseline) Each BPF program uses inline asm (__naked) to force specific register allocation, reads is_fullsock first, then loads the field using the same (or different) register. The test triggers TCP_NEW_SYN_RECV via a TCP handshake and checks that the result is NULL/zero when is_fullsock == 0. Reviewed-by: Sun Jian <sun.jian.kdev@gmail.com> Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> Acked-by: Martin KaFai Lau <martin.lau@kernel.org> Link: https://patch.msgid.link/20260407022720.162151-3-jiayuan.chen@linux.dev Signed-off-by: Jakub Kicinski <kuba@kernel.org>
118 lines
3.1 KiB
C
118 lines
3.1 KiB
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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/*
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* Test the SOCK_OPS_GET_SK() and SOCK_OPS_GET_FIELD() macros in
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* sock_ops_convert_ctx_access() when dst_reg == src_reg.
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*
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* When dst_reg == src_reg, the macros borrow a temporary register to load
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* is_fullsock / is_locked_tcp_sock, because dst_reg holds the ctx pointer
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* and cannot be clobbered before ctx->sk / ctx->field is read. If
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* is_fullsock == 0 (e.g., TCP_NEW_SYN_RECV with a request_sock), the macro
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* must still zero dst_reg so the verifier's PTR_TO_SOCKET_OR_NULL /
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* SCALAR_VALUE type is correct at runtime. A missing clear leaves a stale
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* ctx pointer in dst_reg that passes NULL checks (GET_SK) or leaks a kernel
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* address as a scalar (GET_FIELD).
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*
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* When dst_reg != src_reg, dst_reg itself is used to load is_fullsock, so
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* the JEQ (dst_reg == 0) naturally leaves it zeroed on the !fullsock path.
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*/
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int bug_detected;
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int null_seen;
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SEC("sockops")
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__naked void sock_ops_get_sk_same_reg(void)
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{
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asm volatile (
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"r7 = *(u32 *)(r1 + %[is_fullsock_off]);"
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"r1 = *(u64 *)(r1 + %[sk_off]);"
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"if r7 != 0 goto 2f;"
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"if r1 == 0 goto 1f;"
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"r1 = %[bug_detected] ll;"
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"r2 = 1;"
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"*(u32 *)(r1 + 0) = r2;"
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"goto 2f;"
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"1:"
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"r1 = %[null_seen] ll;"
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"r2 = 1;"
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"*(u32 *)(r1 + 0) = r2;"
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"2:"
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"r0 = 1;"
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"exit;"
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:
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: __imm_const(is_fullsock_off, offsetof(struct bpf_sock_ops, is_fullsock)),
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__imm_const(sk_off, offsetof(struct bpf_sock_ops, sk)),
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__imm_addr(bug_detected),
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__imm_addr(null_seen)
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: __clobber_all);
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}
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/* SOCK_OPS_GET_FIELD: same-register, is_locked_tcp_sock == 0 path. */
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int field_bug_detected;
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int field_null_seen;
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SEC("sockops")
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__naked void sock_ops_get_field_same_reg(void)
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{
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asm volatile (
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"r7 = *(u32 *)(r1 + %[is_fullsock_off]);"
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"r1 = *(u32 *)(r1 + %[snd_cwnd_off]);"
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"if r7 != 0 goto 2f;"
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"if r1 == 0 goto 1f;"
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"r1 = %[field_bug_detected] ll;"
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"r2 = 1;"
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"*(u32 *)(r1 + 0) = r2;"
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"goto 2f;"
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"1:"
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"r1 = %[field_null_seen] ll;"
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"r2 = 1;"
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"*(u32 *)(r1 + 0) = r2;"
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"2:"
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"r0 = 1;"
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"exit;"
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:
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: __imm_const(is_fullsock_off, offsetof(struct bpf_sock_ops, is_fullsock)),
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__imm_const(snd_cwnd_off, offsetof(struct bpf_sock_ops, snd_cwnd)),
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__imm_addr(field_bug_detected),
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__imm_addr(field_null_seen)
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: __clobber_all);
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}
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/* SOCK_OPS_GET_SK: different-register, is_fullsock == 0 path. */
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int diff_reg_bug_detected;
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int diff_reg_null_seen;
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SEC("sockops")
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__naked void sock_ops_get_sk_diff_reg(void)
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{
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asm volatile (
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"r7 = r1;"
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"r6 = *(u32 *)(r7 + %[is_fullsock_off]);"
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"r2 = *(u64 *)(r7 + %[sk_off]);"
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"if r6 != 0 goto 2f;"
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"if r2 == 0 goto 1f;"
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"r1 = %[diff_reg_bug_detected] ll;"
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"r3 = 1;"
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"*(u32 *)(r1 + 0) = r3;"
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"goto 2f;"
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"1:"
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"r1 = %[diff_reg_null_seen] ll;"
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"r3 = 1;"
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"*(u32 *)(r1 + 0) = r3;"
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"2:"
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"r0 = 1;"
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"exit;"
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:
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: __imm_const(is_fullsock_off, offsetof(struct bpf_sock_ops, is_fullsock)),
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__imm_const(sk_off, offsetof(struct bpf_sock_ops, sk)),
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__imm_addr(diff_reg_bug_detected),
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__imm_addr(diff_reg_null_seen)
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: __clobber_all);
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}
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char _license[] SEC("license") = "GPL";
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