From: Cupertino Miranda <cupertino.miranda@oracle.com>
Date: Mon, 6 May 2024 14:18:48 +0000 (+0100)
Subject: bpf/verifier: relax MUL range computation check
X-Git-Tag: v6.10-rc1~153^2~13^2~26^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=41d047a871062f1a4d1871a1908d380c14e75428;p=thirdparty%2Fkernel%2Flinux.git

bpf/verifier: relax MUL range computation check

MUL instruction required that src_reg would be a known value (i.e.
src_reg would be a const value). The condition in this case can be
relaxed, since the range computation algorithm used in current code
already supports a proper range computation for any valid range value on
its operands.

Signed-off-by: Cupertino Miranda <cupertino.miranda@oracle.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: David Faust <david.faust@oracle.com>
Cc: Jose Marchesi <jose.marchesi@oracle.com>
Cc: Elena Zannoni <elena.zannoni@oracle.com>
Link: https://lore.kernel.org/r/20240506141849.185293-6-cupertino.miranda@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1f6deb3e44c50..9e3aba08984e8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13902,12 +13902,8 @@ static bool is_safe_to_compute_dst_reg_range(struct bpf_insn *insn,
 	case BPF_AND:
 	case BPF_XOR:
 	case BPF_OR:
-		return true;
-
-	/* Compute range for the following only if the src_reg is const.
-	 */
 	case BPF_MUL:
-		return src_is_const;
+		return true;
 
 	/* Shift operators range is only computable if shift dimension operand
 	 * is a constant. Shifts greater than 31 or 63 are undefined. This