linux-kernel - [PATCH 4.14 37/47] bpf/verifier: disallow pointer subtraction

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210608175931.695295703@linuxfoundation.org>
Date:   Tue,  8 Jun 2021 20:27:20 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jann Horn <jannh@...gle.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Frank van der Linden <fllinden@...zon.com>
Subject: [PATCH 4.14 37/47] bpf/verifier: disallow pointer subtraction

From: Alexei Starovoitov <ast@...nel.org>

commit dd066823db2ac4e22f721ec85190817b58059a54 upstream.

Subtraction of pointers was accidentally allowed for unpriv programs
by commit 82abbf8d2fc4. Revert that part of commit.

Fixes: 82abbf8d2fc4 ("bpf: do not allow root to mangle valid pointers")
Reported-by: Jann Horn <jannh@...gle.com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
[fllinden@...zon.com: backport to 4.14]
Signed-off-by: Frank van der Linden <fllinden@...zon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/bpf/verifier.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2754,7 +2754,7 @@ static int adjust_reg_min_max_vals(struc
 				 * an arbitrary scalar. Disallow all math except
 				 * pointer subtraction
 				 */
-				if (opcode == BPF_SUB){
+				if (opcode == BPF_SUB && env->allow_ptr_leaks) {
 					mark_reg_unknown(regs, insn->dst_reg);
 					return 0;
 				}