83 lines
2.7 KiB
Diff
83 lines
2.7 KiB
Diff
From: Jann Horn <jannh@google.com>
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Date: Mon, 18 Dec 2017 20:11:56 -0800
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Subject: [4/9] bpf: fix 32-bit ALU op verification
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Origin: https://git.kernel.org/linus/468f6eafa6c44cb2c5d8aad35e12f06c240a812a
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32-bit ALU ops operate on 32-bit values and have 32-bit outputs.
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Adjust the verifier accordingly.
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Fixes: f1174f77b50c ("bpf/verifier: rework value tracking")
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Signed-off-by: Jann Horn <jannh@google.com>
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Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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---
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kernel/bpf/verifier.c | 28 +++++++++++++++++-----------
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1 file changed, 17 insertions(+), 11 deletions(-)
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--- a/kernel/bpf/verifier.c
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+++ b/kernel/bpf/verifier.c
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@@ -2010,6 +2010,10 @@ static int adjust_ptr_min_max_vals(struc
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return 0;
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}
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+/* WARNING: This function does calculations on 64-bit values, but the actual
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+ * execution may occur on 32-bit values. Therefore, things like bitshifts
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+ * need extra checks in the 32-bit case.
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+ */
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static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
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struct bpf_insn *insn,
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struct bpf_reg_state *dst_reg,
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@@ -2020,12 +2024,8 @@ static int adjust_scalar_min_max_vals(st
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bool src_known, dst_known;
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s64 smin_val, smax_val;
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u64 umin_val, umax_val;
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+ u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
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- if (BPF_CLASS(insn->code) != BPF_ALU64) {
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- /* 32-bit ALU ops are (32,32)->64 */
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- coerce_reg_to_size(dst_reg, 4);
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- coerce_reg_to_size(&src_reg, 4);
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- }
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smin_val = src_reg.smin_value;
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smax_val = src_reg.smax_value;
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umin_val = src_reg.umin_value;
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@@ -2161,9 +2161,9 @@ static int adjust_scalar_min_max_vals(st
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__update_reg_bounds(dst_reg);
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break;
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case BPF_LSH:
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- if (umax_val > 63) {
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- /* Shifts greater than 63 are undefined. This includes
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- * shifts by a negative number.
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+ if (umax_val >= insn_bitness) {
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+ /* Shifts greater than 31 or 63 are undefined.
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+ * This includes shifts by a negative number.
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*/
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mark_reg_unknown(env, regs, insn->dst_reg);
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break;
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@@ -2189,9 +2189,9 @@ static int adjust_scalar_min_max_vals(st
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__update_reg_bounds(dst_reg);
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break;
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case BPF_RSH:
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- if (umax_val > 63) {
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- /* Shifts greater than 63 are undefined. This includes
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- * shifts by a negative number.
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+ if (umax_val >= insn_bitness) {
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+ /* Shifts greater than 31 or 63 are undefined.
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+ * This includes shifts by a negative number.
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*/
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mark_reg_unknown(env, regs, insn->dst_reg);
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break;
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@@ -2227,6 +2227,12 @@ static int adjust_scalar_min_max_vals(st
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break;
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}
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+ if (BPF_CLASS(insn->code) != BPF_ALU64) {
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+ /* 32-bit ALU ops are (32,32)->32 */
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+ coerce_reg_to_size(dst_reg, 4);
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+ coerce_reg_to_size(&src_reg, 4);
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+ }
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+
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__reg_deduce_bounds(dst_reg);
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__reg_bound_offset(dst_reg);
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return 0;
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