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From: Frank van der Linden <fllinden@amazon.com>
To: <stable@vger.kernel.org>
Cc: <bpf@vger.kernel.org>, <daniel@iogearbox.net>
Subject: [PATCH v2 4.14 11/17] bpf/verifier: disallow pointer subtraction
Date: Mon, 31 May 2021 18:25:50 +0000	[thread overview]
Message-ID: <20210531182556.25277-12-fllinden@amazon.com> (raw)
In-Reply-To: <20210531182556.25277-1-fllinden@amazon.com>

From: Alexei Starovoitov <ast@kernel.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@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
[fllinden@amazon.com: backport to 4.14]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b999e268ee23..5c440398e0a1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2754,7 +2754,7 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				 * 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;
 				}
-- 
2.23.4


  parent reply	other threads:[~2021-05-31 18:26 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-31 18:25 [PATCH v2 4.14 00/16] CVE fixes and selftests cleanup Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 01/17] bpf, selftests: Fix up some test_verifier cases for unprivileged Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 02/17] bpf: Move off_reg into sanitize_ptr_alu Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 03/17] bpf: Ensure off_reg has no mixed signed bounds for all types Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 04/17] bpf: Rework ptr_limit into alu_limit and add common error path Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 05/17] bpf: Improve verifier error messages for users Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 06/17] bpf: Refactor and streamline bounds check into helper Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 07/17] bpf: Move sanitize_val_alu out of op switch Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 08/17] bpf: Tighten speculative pointer arithmetic mask Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 09/17] bpf: Update selftests to reflect new error states Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 10/17] bpf: do not allow root to mangle valid pointers Frank van der Linden
2021-05-31 18:25 ` Frank van der Linden [this message]
2021-05-31 18:25 ` [PATCH v2 4.14 12/17] selftests/bpf: fix test_align Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 13/17] selftests/bpf: make 'dubious pointer arithmetic' test useful Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 14/17] bpf: Fix leakage of uninitialized bpf stack under speculation Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 15/17] bpf: Wrap aux data inside bpf_sanitize_info container Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 16/17] bpf: Fix mask direction swap upon off reg sign change Frank van der Linden
2021-05-31 18:25 ` [PATCH v2 4.14 17/17] bpf: No need to simulate speculative domain for immediates Frank van der Linden
2021-06-08 14:48 ` [PATCH v2 4.14 00/16] CVE fixes and selftests cleanup Greg KH

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