70 lines
2.6 KiB
Diff
70 lines
2.6 KiB
Diff
From 3c5659ffcc9d2497045dda465a35720f78314e87 Mon Sep 17 00:00:00 2001
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From: Jann Horn <jannh@google.com>
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Date: Thu, 4 Jan 2018 08:01:21 -0600
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Subject: [PATCH 226/231] UBUNTU: SAUCE: bpf: reject out-of-bounds stack
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pointer calculation
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Reject programs that compute wildly out-of-bounds stack pointers.
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Otherwise, pointers can be computed with an offset that doesn't fit into an
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`int`, causing security issues in the stack memory access check (as well as
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signed integer overflow during offset addition).
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This is a fix specifically for the v4.9 stable tree because the mainline
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code looks very different at this point.
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Fixes: 7bca0a9702edf ("bpf: enhance verifier to understand stack pointer arithmetic")
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Signed-off-by: Jann Horn <jannh@google.com>
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Acked-by: Daniel Borkmann <daniel@iogearbox.net>
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CVE-2017-17863
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Link: https://www.spinics.net/lists/stable/msg206985.html
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Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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(cherry picked from commit 1c26ffd0e9b24d512824cabc6687a14d4777d0f3)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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kernel/bpf/verifier.c | 22 ++++++++++++++++++++--
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1 file changed, 20 insertions(+), 2 deletions(-)
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diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
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index 3940019b9740..4321625fe32a 100644
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2122,10 +2122,28 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
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((BPF_SRC(insn->code) == BPF_X &&
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regs[insn->src_reg].type == CONST_IMM) ||
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BPF_SRC(insn->code) == BPF_K)) {
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- if (BPF_SRC(insn->code) == BPF_X)
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+ if (BPF_SRC(insn->code) == BPF_X) {
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+ /* check in case the register contains a big
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+ * 64-bit value
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+ */
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+ if (regs[insn->src_reg].imm < -MAX_BPF_STACK ||
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+ regs[insn->src_reg].imm > MAX_BPF_STACK) {
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+ verbose("R%d value too big in R%d pointer arithmetic\n",
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+ insn->src_reg, insn->dst_reg);
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+ return -EACCES;
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+ }
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dst_reg->imm += regs[insn->src_reg].imm;
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- else
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+ } else {
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+ /* safe against overflow: addition of 32-bit
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+ * numbers in 64-bit representation
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+ */
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dst_reg->imm += insn->imm;
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+ }
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+ if (dst_reg->imm > 0 || dst_reg->imm < -MAX_BPF_STACK) {
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+ verbose("R%d out-of-bounds pointer arithmetic\n",
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+ insn->dst_reg);
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+ return -EACCES;
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+ }
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return 0;
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} else if (opcode == BPF_ADD &&
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BPF_CLASS(insn->code) == BPF_ALU64 &&
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--
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2.14.2
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