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76 lines
2.9 KiB
Diff
76 lines
2.9 KiB
Diff
From 0d0e57697f162da4aa218b5feafe614fb666db07 Mon Sep 17 00:00:00 2001
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From: Daniel Borkmann <daniel@iogearbox.net>
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Date: Mon, 8 May 2017 00:04:09 +0200
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Subject: [PATCH] bpf: don't let ldimm64 leak map addresses on unprivileged
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The patch fixes two things at once:
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1) It checks the env->allow_ptr_leaks and only prints the map address to
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the log if we have the privileges to do so, otherwise it just dumps 0
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as we would when kptr_restrict is enabled on %pK. Given the latter is
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off by default and not every distro sets it, I don't want to rely on
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this, hence the 0 by default for unprivileged.
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2) Printing of ldimm64 in the verifier log is currently broken in that
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we don't print the full immediate, but only the 32 bit part of the
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first insn part for ldimm64. Thus, fix this up as well; it's okay to
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access, since we verified all ldimm64 earlier already (including just
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constants) through replace_map_fd_with_map_ptr().
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Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")
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Fixes: cbd357008604 ("bpf: verifier (add ability to receive verification log)")
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Reported-by: Jann Horn <jannh@google.com>
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Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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Acked-by: Alexei Starovoitov <ast@kernel.org>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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kernel/bpf/verifier.c | 21 ++++++++++++++++-----
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1 file changed, 16 insertions(+), 5 deletions(-)
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diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
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index c2ff608c1984e..c5b56c92f8e25 100644
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -298,7 +298,8 @@ static const char *const bpf_jmp_string[16] = {
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[BPF_EXIT >> 4] = "exit",
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};
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-static void print_bpf_insn(struct bpf_insn *insn)
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+static void print_bpf_insn(const struct bpf_verifier_env *env,
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+ const struct bpf_insn *insn)
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{
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u8 class = BPF_CLASS(insn->code);
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@@ -362,9 +363,19 @@ static void print_bpf_insn(struct bpf_insn *insn)
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insn->code,
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bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
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insn->src_reg, insn->imm);
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- } else if (BPF_MODE(insn->code) == BPF_IMM) {
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- verbose("(%02x) r%d = 0x%x\n",
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- insn->code, insn->dst_reg, insn->imm);
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+ } else if (BPF_MODE(insn->code) == BPF_IMM &&
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+ BPF_SIZE(insn->code) == BPF_DW) {
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+ /* At this point, we already made sure that the second
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+ * part of the ldimm64 insn is accessible.
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+ */
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+ u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
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+ bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD;
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+
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+ if (map_ptr && !env->allow_ptr_leaks)
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+ imm = 0;
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+
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+ verbose("(%02x) r%d = 0x%llx\n", insn->code,
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+ insn->dst_reg, (unsigned long long)imm);
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} else {
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verbose("BUG_ld_%02x\n", insn->code);
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return;
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@@ -2853,7 +2864,7 @@ static int do_check(struct bpf_verifier_env *env)
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if (log_level) {
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verbose("%d: ", insn_idx);
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- print_bpf_insn(insn);
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+ print_bpf_insn(env, insn);
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}
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err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);
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