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authorDaniel Borkmann <daniel@iogearbox.net>2021-05-28 16:47:27 +0300
committerDaniel Borkmann <daniel@iogearbox.net>2021-06-15 00:06:06 +0300
commitfe9a5ca7e370e613a9a75a13008a3845ea759d6e (patch)
tree6c6981a0c4ce376319b687a1f9ef9e98619dd9e8 /kernel
parentd203b0fd863a2261e5d00b97f3d060c4c2a6db71 (diff)
downloadlinux-fe9a5ca7e370e613a9a75a13008a3845ea759d6e.tar.xz
bpf: Do not mark insn as seen under speculative path verification
... in such circumstances, we do not want to mark the instruction as seen given the goal is still to jmp-1 rewrite/sanitize dead code, if it is not reachable from the non-speculative path verification. We do however want to verify it for safety regardless. With the patch as-is all the insns that have been marked as seen before the patch will also be marked as seen after the patch (just with a potentially different non-zero count). An upcoming patch will also verify paths that are unreachable in the non-speculative domain, hence this extension is needed. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: John Fastabend <john.fastabend@gmail.com> Reviewed-by: Benedict Schlueter <benedict.schlueter@rub.de> Reviewed-by: Piotr Krysiuk <piotras@gmail.com> Acked-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f93c7befb5dc..af88d9b9c014 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6572,6 +6572,19 @@ do_sim:
return !ret ? REASON_STACK : 0;
}
+static void sanitize_mark_insn_seen(struct bpf_verifier_env *env)
+{
+ struct bpf_verifier_state *vstate = env->cur_state;
+
+ /* If we simulate paths under speculation, we don't update the
+ * insn as 'seen' such that when we verify unreachable paths in
+ * the non-speculative domain, sanitize_dead_code() can still
+ * rewrite/sanitize them.
+ */
+ if (!vstate->speculative)
+ env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
+}
+
static int sanitize_err(struct bpf_verifier_env *env,
const struct bpf_insn *insn, int reason,
const struct bpf_reg_state *off_reg,
@@ -10630,7 +10643,7 @@ static int do_check(struct bpf_verifier_env *env)
}
regs = cur_regs(env);
- env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
+ sanitize_mark_insn_seen(env);
prev_insn_idx = env->insn_idx;
if (class == BPF_ALU || class == BPF_ALU64) {
@@ -10857,7 +10870,7 @@ process_bpf_exit:
return err;
env->insn_idx++;
- env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
+ sanitize_mark_insn_seen(env);
} else {
verbose(env, "invalid BPF_LD mode\n");
return -EINVAL;
@@ -12712,6 +12725,9 @@ static void free_states(struct bpf_verifier_env *env)
* insn_aux_data was touched. These variables are compared to clear temporary
* data from failed pass. For testing and experiments do_check_common() can be
* run multiple times even when prior attempt to verify is unsuccessful.
+ *
+ * Note that special handling is needed on !env->bypass_spec_v1 if this is
+ * ever called outside of error path with subsequent program rejection.
*/
static void sanitize_insn_aux_data(struct bpf_verifier_env *env)
{