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authorDaniel Borkmann <daniel@iogearbox.net>2017-12-22 16:29:05 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-12-25 14:23:47 +0100
commit3695b3b18519099224efbc5875569d2cb6da256d (patch)
tree03b70a41cbc9ddd7f4f9b11c2b95c3035b0aa8cc /kernel/bpf
parentd75d3ee237cee9068022117e059b64bbab617f3d (diff)
bpf: fix incorrect sign extension in check_alu_op()
From: Jann Horn <jannh@google.com> [ Upstream commit 95a762e2c8c942780948091f8f2a4f32fce1ac6f ] 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> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b03af36b8e87..8b1ebe4c6aba 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1790,10 +1790,17 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
/* case: R = imm
* remember the value we stored into this reg
*/
+ u64 imm;
+
+ if (BPF_CLASS(insn->code) == BPF_ALU64)
+ imm = insn->imm;
+ else
+ imm = (u32)insn->imm;
+
regs[insn->dst_reg].type = CONST_IMM;
- regs[insn->dst_reg].imm = insn->imm;
- regs[insn->dst_reg].max_value = insn->imm;
- regs[insn->dst_reg].min_value = insn->imm;
+ regs[insn->dst_reg].imm = imm;
+ regs[insn->dst_reg].max_value = imm;
+ regs[insn->dst_reg].min_value = imm;
}
} else if (opcode > BPF_END) {