From: Daniel Borkmann <daniel@iogearbox.net>
To: ast@kernel.org
Cc: jannh@google.com, davem@davemloft.net,
jakub.kicinski@netronome.com, netdev@vger.kernel.org,
Daniel Borkmann <daniel@iogearbox.net>
Subject: [PATCH bpf v3 6/9] bpf: restrict unknown scalars of mixed signed bounds for unprivileged
Date: Thu, 3 Jan 2019 00:58:32 +0100 [thread overview]
Message-ID: <20190102235835.3311-7-daniel@iogearbox.net> (raw)
In-Reply-To: <20190102235835.3311-1-daniel@iogearbox.net>
For unknown scalars of mixed signed bounds, meaning their smin_value is
negative and their smax_value is positive, we need to reject arithmetic
with pointer to map value. For unprivileged the goal is to mask every
map pointer arithmetic and this cannot reliably be done when it is
unknown at verification time whether the scalar value is negative or
positive. Given this is a corner case, the likelihood of breaking should
be very small.
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/verifier.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9ac205d..eebbc03 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3081,8 +3081,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
+ u32 dst = insn->dst_reg, src = insn->src_reg;
u8 opcode = BPF_OP(insn->code);
- u32 dst = insn->dst_reg;
dst_reg = ®s[dst];
@@ -3115,6 +3115,13 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
verbose(env, "R%d pointer arithmetic on %s prohibited\n",
dst, reg_type_str[ptr_reg->type]);
return -EACCES;
+ case PTR_TO_MAP_VALUE:
+ if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
+ verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
+ off_reg == dst_reg ? dst : src);
+ return -EACCES;
+ }
+ /* fall-through */
default:
break;
}
--
2.9.5
next prev parent reply other threads:[~2019-01-02 23:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-02 23:58 [PATCH bpf v3 0/9] bpf fix to prevent oob under speculation Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 1/9] bpf: move {prev_,}insn_idx into verifier env Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 2/9] bpf: move tmp variable into ax register in interpreter Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 3/9] bpf: enable access to ax register also from verifier rewrite Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 4/9] bpf: restrict map value pointer arithmetic for unprivileged Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 5/9] bpf: restrict stack " Daniel Borkmann
2019-01-02 23:58 ` Daniel Borkmann [this message]
2019-01-02 23:58 ` [PATCH bpf v3 7/9] bpf: fix check_map_access smin_value test when pointer contains offset Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 8/9] bpf: prevent out of bounds speculation on pointer arithmetic Daniel Borkmann
2019-01-03 21:13 ` Jann Horn
2019-01-03 23:22 ` Daniel Borkmann
2019-01-02 23:58 ` [PATCH bpf v3 9/9] bpf: add various test cases to selftests Daniel Borkmann
2019-01-03 0:08 ` [PATCH bpf v3 0/9] bpf fix to prevent oob under speculation Alexei Starovoitov
2019-01-22 14:36 ` stable backport for the BPF speculation series? [was: Re: [PATCH bpf v3 0/9] bpf fix to prevent oob under speculation] Jann Horn
2019-01-22 16:44 ` stable backport for the BPF speculation series? David Miller
2019-01-23 1:55 ` Daniel Borkmann
2019-01-23 17:04 ` stable backport for the BPF speculation series? [was: Re: [PATCH bpf v3 0/9] bpf fix to prevent oob under speculation] Greg Kroah-Hartman
2019-01-23 17:12 ` Jann Horn
2019-01-24 11:53 ` Daniel Borkmann
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