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[PATCHv5,net-next,07/15] bpf: recognize 64bit immediate loads as consts

Message ID 1474018622-10653-8-git-send-email-jakub.kicinski@netronome.com
State Superseded, archived
Delegated to: David Miller
Headers show

Commit Message

Jakub Kicinski Sept. 16, 2016, 9:36 a.m. UTC 
When running as parser interpret BPF_LD | BPF_IMM | BPF_DW
instructions as loading CONST_IMM with the value stored
in imm.  The verifier will continue not recognizing those
due to concerns about search space/program complexity
increase.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
v3:
 - limit to parsers.
---
 kernel/bpf/verifier.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Comments

Daniel Borkmann Sept. 16, 2016, 9:37 p.m. UTC | #1 
On 09/16/2016 11:36 AM, Jakub Kicinski wrote:
> When running as parser interpret BPF_LD | BPF_IMM | BPF_DW
> instructions as loading CONST_IMM with the value stored
> in imm.  The verifier will continue not recognizing those
> due to concerns about search space/program complexity
> increase.
>
> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Acked-by: Alexei Starovoitov <ast@kernel.org>

Acked-by: Daniel Borkmann <daniel@iogearbox.net>
diff mbox

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d93e78331b90..f5bed7cce08d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1766,9 +1766,19 @@  static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	if (err)
 		return err;
 
-	if (insn->src_reg == 0)
-		/* generic move 64-bit immediate into a register */
+	if (insn->src_reg == 0) {
+		/* generic move 64-bit immediate into a register,
+		 * only analyzer needs to collect the ld_imm value.
+		 */
+		u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
+
+		if (!env->analyzer_ops)
+			return 0;
+
+		regs[insn->dst_reg].type = CONST_IMM;
+		regs[insn->dst_reg].imm = imm;
 		return 0;
+	}
 
 	/* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
 	BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);