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 <[email protected]> --- tools/testing/selftests/bpf/prog_tests/verifier.c | 2 + .../selftests/bpf/progs/verifier_flow_keys.c | 97 ++++++++++++++++++++++ 2 files changed, 99 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c index 89779d897aba..8a3d69e2453c 100644 --- a/tools/testing/selftests/bpf/prog_tests/verifier.c +++ b/tools/testing/selftests/bpf/prog_tests/verifier.c @@ -38,6 +38,7 @@ #include "verifier_div0.skel.h" #include "verifier_div_mod_bounds.skel.h" #include "verifier_div_overflow.skel.h" +#include "verifier_flow_keys.skel.h" #include "verifier_global_subprogs.skel.h" #include "verifier_global_ptr_args.skel.h" #include "verifier_gotol.skel.h" @@ -190,6 +191,7 @@ void test_verifier_direct_stack_access_wraparound(void) { RUN(verifier_direct_st void test_verifier_div0(void) { RUN(verifier_div0); } void test_verifier_div_mod_bounds(void) { RUN(verifier_div_mod_bounds); } void test_verifier_div_overflow(void) { RUN(verifier_div_overflow); } +void test_verifier_flow_keys(void) { RUN(verifier_flow_keys); } void test_verifier_global_subprogs(void) { RUN(verifier_global_subprogs); } void test_verifier_global_ptr_args(void) { RUN(verifier_global_ptr_args); } void test_verifier_gotol(void) { RUN(verifier_gotol); } diff --git a/tools/testing/selftests/bpf/progs/verifier_flow_keys.c b/tools/testing/selftests/bpf/progs/verifier_flow_keys.c new file mode 100644 index 000000000000..d780a36a6e9a --- /dev/null +++ b/tools/testing/selftests/bpf/progs/verifier_flow_keys.c @@ -0,0 +1,97 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Bounds checks for PTR_TO_FLOW_KEYS pointer arithmetic. */ + +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h" + +/* sizeof(struct bpf_flow_keys) is well under 4096, so +0x1000 is OOB. */ + +SEC("flow_dissector") +__description("flow_keys: in-bounds constant pointer arithmetic accepted") +__success +__naked void flow_keys_const_inbounds(void) +{ + asm volatile (" \ + r1 = *(u64 *)(r1 + %[flow_keys]); \ + r1 += 8; \ + r0 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ +" : + : __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)) + : __clobber_all); +} + +SEC("flow_dissector") +__description("flow_keys: OOB via constant pointer arithmetic rejected") +__failure __msg("invalid access to flow keys off=4096 size=8") +__naked void flow_keys_const_oob_read(void) +{ + asm volatile (" \ + r1 = *(u64 *)(r1 + %[flow_keys]); \ + r1 += 4096; \ + r0 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ +" : + : __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)) + : __clobber_all); +} + +SEC("flow_dissector") +__description("flow_keys: OOB write via constant pointer arithmetic rejected") +__failure __msg("invalid access to flow keys off=4096 size=8") +__naked void flow_keys_const_oob_write(void) +{ + asm volatile (" \ + r1 = *(u64 *)(r1 + %[flow_keys]); \ + r1 += 4096; \ + r2 = 0; \ + *(u64 *)(r1 + 0) = r2; \ + r0 = 0; \ + exit; \ +" : + : __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)) + : __clobber_all); +} + +/* Equivalent OOB expressed directly in insn->off; this form was always + * rejected and is kept to show both forms now share one diagnostic. + */ +SEC("flow_dissector") +__description("flow_keys: OOB via insn->off rejected") +__failure __msg("invalid access to flow keys off=4096 size=8") +__naked void flow_keys_insn_off_oob(void) +{ + asm volatile (" \ + r1 = *(u64 *)(r1 + %[flow_keys]); \ + r0 = *(u64 *)(r1 + 4096); \ + r0 = 0; \ + exit; \ +" : + : __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)) + : __clobber_all); +} + +SEC("flow_dissector") +__description("flow_keys: variable pointer arithmetic rejected") +__failure __msg("R1 pointer arithmetic on flow_keys prohibited") +__naked void flow_keys_var_read(void) +{ + asm volatile (" \ + r6 = r1; \ + call %[bpf_get_prandom_u32]; \ + r0 &= 0xFFFF; \ + r1 = *(u64 *)(r6 + %[flow_keys]); \ + r1 += r0; \ + r0 = *(u64 *)(r1 + 0); \ + r0 = 0; \ + exit; \ +" : + : __imm_const(flow_keys, offsetof(struct __sk_buff, flow_keys)), + __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +char _license[] SEC("license") = "GPL"; -- 2.34.1
