From: Alexei Starovoitov <ast@kernel.org>
To: "David S . Miller" <davem@davemloft.net>
Cc: Daniel Borkmann <daniel@iogearbox.net>,
Jann Horn <jannh@google.com>, Edward Cree <ecree@solarflare.com>,
<netdev@vger.kernel.org>, <kernel-team@fb.com>
Subject: [PATCH bpf 6/9] bpf: force strict alignment checks for stack pointers
Date: Mon, 18 Dec 2017 20:11:58 -0800 [thread overview]
Message-ID: <20171219041201.1979983-7-ast@kernel.org> (raw)
In-Reply-To: <20171219041201.1979983-1-ast@kernel.org>
From: Jann Horn <jannh@google.com>
Force strict alignment checks for stack pointers because the tracking of
stack spills relies on it; unaligned stack accesses can lead to corruption
of spilled registers, which is exploitable.
Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/verifier.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 77e4b5223867..102c519836f6 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1059,6 +1059,11 @@ static int check_ptr_alignment(struct bpf_verifier_env *env,
break;
case PTR_TO_STACK:
pointer_desc = "stack ";
+ /* The stack spill tracking logic in check_stack_write()
+ * and check_stack_read() relies on stack accesses being
+ * aligned.
+ */
+ strict = true;
break;
default:
break;
--
2.9.5
next prev parent reply other threads:[~2017-12-19 4:12 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-19 4:11 [PATCH bpf 0/9] bpf: verifier security fixes Alexei Starovoitov
2017-12-19 4:11 ` [PATCH bpf 1/9] bpf/verifier: fix bounds calculation on BPF_RSH Alexei Starovoitov
2017-12-19 4:11 ` [PATCH bpf 2/9] bpf: fix incorrect sign extension in check_alu_op() Alexei Starovoitov
2017-12-19 4:11 ` [PATCH bpf 3/9] bpf: fix incorrect tracking of register size truncation Alexei Starovoitov
2017-12-19 4:11 ` [PATCH bpf 4/9] bpf: fix 32-bit ALU op verification Alexei Starovoitov
2017-12-19 4:11 ` [PATCH bpf 5/9] bpf: fix missing error return in check_stack_boundary() Alexei Starovoitov
2017-12-19 4:11 ` Alexei Starovoitov [this message]
2017-12-19 4:11 ` [PATCH bpf 7/9] bpf: don't prune branches when a scalar is replaced with a pointer Alexei Starovoitov
2017-12-19 4:12 ` [PATCH bpf 8/9] bpf: fix integer overflows Alexei Starovoitov
2017-12-19 10:29 ` Edward Cree
2017-12-19 19:57 ` Alexei Starovoitov
2017-12-19 4:12 ` [PATCH bpf 9/9] selftests/bpf: add tests for recent bugfixes Alexei Starovoitov
2017-12-21 2:20 ` [PATCH bpf 0/9] bpf: verifier security fixes Daniel Borkmann
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