diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7a375f608263..9de0ec0c3ed9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -16871,6 +16871,7 @@ static void sync_linked_regs(struct bpf_verifier_state *vstate, struct bpf_reg_s } else { s32 saved_subreg_def = reg->subreg_def; s32 saved_off = reg->off; + u32 saved_id = reg->id; fake_reg.type = SCALAR_VALUE; __mark_reg_known(&fake_reg, (s32)reg->off - (s32)known_reg->off); @@ -16878,10 +16879,11 @@ static void sync_linked_regs(struct bpf_verifier_state *vstate, struct bpf_reg_s /* reg = known_reg; reg += delta */ copy_register_state(reg, known_reg); /* - * Must preserve off, id and add_const flag, + * Must preserve off, id and subreg_def flag, * otherwise another sync_linked_regs() will be incorrect. */ reg->off = saved_off; + reg->id = saved_id; reg->subreg_def = saved_subreg_def; scalar32_min_max_add(reg, &fake_reg); diff --git a/tools/testing/selftests/bpf/progs/verifier_linked_scalars.c b/tools/testing/selftests/bpf/progs/verifier_linked_scalars.c index 8f755d2464cf..5f41bbb730a7 100644 --- a/tools/testing/selftests/bpf/progs/verifier_linked_scalars.c +++ b/tools/testing/selftests/bpf/progs/verifier_linked_scalars.c @@ -31,4 +31,37 @@ l1: \ " ::: __clobber_all); } +/* + * Test that sync_linked_regs() preserves register IDs. + * + * The sync_linked_regs() function copies bounds from known_reg to linked + * registers. When doing so, it must preserve each register's original id + * to allow subsequent syncs from the same source to work correctly. + * + */ +SEC("socket") +__success +__naked void sync_linked_regs_preserves_id(void) +{ + asm volatile (" \ + call %[bpf_get_prandom_u32]; \ + r0 &= 0xff; /* r0 in [0, 255] */ \ + r1 = r0; /* r0, r1 linked with id 1 */ \ + r1 += 4; /* r1 has id=1 and off=4 in [4, 259] */ \ + if r1 < 10 goto l0_%=; \ + /* r1 in [10, 259], r0 synced to [6, 255] */ \ + r2 = r0; /* r2 has id=1 and in [6, 255] */ \ + if r1 < 14 goto l0_%=; \ + /* r1 in [14, 259], r0 synced to [10, 255] */ \ + if r0 >= 10 goto l0_%=; \ + /* Never executed */ \ + r0 /= 0; \ +l0_%=: \ + r0 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + char _license[] SEC("license") = "GPL";