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 2/9] bpf: fix incorrect sign extension in check_alu_op()
Date: Mon, 18 Dec 2017 20:11:54 -0800 [thread overview]
Message-ID: <20171219041201.1979983-3-ast@kernel.org> (raw)
In-Reply-To: <20171219041201.1979983-1-ast@kernel.org>
From: Jann Horn <jannh@google.com>
Distinguish between
BPF_ALU64|BPF_MOV|BPF_K (load 32-bit immediate, sign-extended to 64-bit)
and BPF_ALU|BPF_MOV|BPF_K (load 32-bit immediate, zero-padded to 64-bit);
only perform sign extension in the first case.
Starting with v4.14, this is exploitable by unprivileged users as long as
the unprivileged_bpf_disabled sysctl isn't set.
Debian assigned CVE-2017-16995 for this issue.
v3:
- add CVE number (Ben Hutchings)
Fixes: 484611357c19 ("bpf: allow access into map value arrays")
Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
kernel/bpf/verifier.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 625e358ca765..c086010ae51e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2408,7 +2408,13 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
* remember the value we stored into this reg
*/
regs[insn->dst_reg].type = SCALAR_VALUE;
- __mark_reg_known(regs + insn->dst_reg, insn->imm);
+ if (BPF_CLASS(insn->code) == BPF_ALU64) {
+ __mark_reg_known(regs + insn->dst_reg,
+ insn->imm);
+ } else {
+ __mark_reg_known(regs + insn->dst_reg,
+ (u32)insn->imm);
+ }
}
} else if (opcode > BPF_END) {
--
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 ` Alexei Starovoitov [this message]
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 ` [PATCH bpf 6/9] bpf: force strict alignment checks for stack pointers Alexei Starovoitov
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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