From: Eduard Zingerman <eddyz87@gmail.com>
To: Andrii Nakryiko <andrii@kernel.org>,
bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net,
martin.lau@kernel.org
Cc: kernel-team@meta.com
Subject: Re: [PATCH v3 bpf-next 03/10] bpf: fix check for attempt to corrupt spilled pointer
Date: Tue, 05 Dec 2023 00:12:30 +0200 [thread overview]
Message-ID: <3fca38fdfd975f735e3dd31930637cfbc70948f4.camel@gmail.com> (raw)
In-Reply-To: <20231204192601.2672497-4-andrii@kernel.org>
On Mon, 2023-12-04 at 11:25 -0800, Andrii Nakryiko wrote:
[...]
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 4f8a3c77eb80..73315e2f20d9 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -4431,7 +4431,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
> * so it's aligned access and [off, off + size) are within stack limits
> */
> if (!env->allow_ptr_leaks &&
> - state->stack[spi].slot_type[0] == STACK_SPILL &&
> + is_spilled_reg(&state->stack[spi]) &&
> size != BPF_REG_SIZE) {
> verbose(env, "attempt to corrupt spilled pointer on stack\n");
> return -EACCES;
I think there is a small detail here.
slot_type[0] == STACK_SPILL actually checks if a spill is 64-bit.
Thus, with this patch applied the test below does not pass.
Log fragment:
1: (57) r0 &= 65535 ; R0_w=scalar(...,var_off=(0x0; 0xffff))
2: (63) *(u32 *)(r10 -8) = r0
3: R0_w=scalar(...,var_off=(0x0; 0xffff)) R10=fp0 fp-8=mmmmscalar(...,var_off=(0x0; 0xffff))
3: (b7) r0 = 42 ; R0_w=42
4: (63) *(u32 *)(r10 -4) = r0
attempt to corrupt spilled pointer on stack
Admittedly, this happens only when the only capability is CAP_BPF and
we don't test this configuration.
---
iff --git a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
index 359df865a8f3..61ada86e84df 100644
--- a/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
+++ b/tools/testing/selftests/bpf/progs/verifier_basic_stack.c
@@ -97,4 +97,20 @@ __naked void misaligned_read_from_stack(void)
" ::: __clobber_all);
}
+SEC("socket")
+__success_unpriv
+__naked void spill_lo32_write_hi32(void)
+{
+ asm volatile (" \
+ call %[bpf_get_prandom_u32]; \
+ r0 &= 0xffff; \
+ *(u32*)(r10 - 8) = r0; \
+ r0 = 42; \
+ *(u32*)(r10 - 4) = r0; \
+ exit; \
+" :
+ : __imm(bpf_get_prandom_u32)
+ : __clobber_all);
+}
+
char _license[] SEC("license") = "GPL";
diff --git a/tools/testing/selftests/bpf/test_loader.c b/tools/testing/selftests/bpf/test_loader.c
index a350ecdfba4a..a5ad6b01175e 100644
--- a/tools/testing/selftests/bpf/test_loader.c
+++ b/tools/testing/selftests/bpf/test_loader.c
@@ -430,7 +430,7 @@ struct cap_state {
static int drop_capabilities(struct cap_state *caps)
{
const __u64 caps_to_drop = (1ULL << CAP_SYS_ADMIN | 1ULL << CAP_NET_ADMIN |
- 1ULL << CAP_PERFMON | 1ULL << CAP_BPF);
+ 1ULL << CAP_PERFMON /*| 1ULL << CAP_BPF */);
int err;
err = cap_disable_effective(caps_to_drop, &caps->old_caps);
next prev parent reply other threads:[~2023-12-04 22:12 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-04 19:25 [PATCH v3 bpf-next 00/10] Complete BPF verifier precision tracking support for register spills Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 01/10] bpf: support non-r10 register spill/fill to/from stack in precision tracking Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 02/10] selftests/bpf: add stack access precision test Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 03/10] bpf: fix check for attempt to corrupt spilled pointer Andrii Nakryiko
2023-12-04 22:12 ` Eduard Zingerman [this message]
2023-12-04 22:15 ` Eduard Zingerman
2023-12-05 0:23 ` Andrii Nakryiko
2023-12-05 0:54 ` Eduard Zingerman
2023-12-05 3:56 ` Andrii Nakryiko
2023-12-05 13:34 ` Eduard Zingerman
2023-12-05 18:30 ` Andrii Nakryiko
2023-12-05 18:49 ` Eduard Zingerman
2023-12-05 18:55 ` Andrii Nakryiko
2023-12-05 1:45 ` Alexei Starovoitov
2023-12-05 3:50 ` Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 04/10] bpf: preserve STACK_ZERO slots on partial reg spills Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 05/10] selftests/bpf: validate STACK_ZERO is preserved on subreg spill Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 06/10] bpf: preserve constant zero when doing partial register restore Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 07/10] selftests/bpf: validate zero preservation for sub-slot loads Andrii Nakryiko
2023-12-04 19:25 ` [PATCH v3 bpf-next 08/10] bpf: track aligned STACK_ZERO cases as imprecise spilled registers Andrii Nakryiko
2023-12-04 19:26 ` [PATCH v3 bpf-next 09/10] selftests/bpf: validate precision logic in partial_stack_load_preserves_zeros Andrii Nakryiko
2023-12-04 19:26 ` [PATCH v3 bpf-next 10/10] bpf: use common instruction history across all states Andrii Nakryiko
2023-12-04 22:32 ` [PATCH v3 bpf-next 00/10] Complete BPF verifier precision tracking support for register spills Andrii Nakryiko
2023-12-04 23:02 ` Yonghong Song
2023-12-04 23:52 ` Andrii Nakryiko
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