BPF Archive on lore.kernel.org
 help / color / Atom feed
From: Frank van der Linden <fllinden@amazon.com>
To: <stable@vger.kernel.org>
Cc: <bpf@vger.kernel.org>
Subject: [PATCH 5.4 3/8] bpf: Rework ptr_limit into alu_limit and add common error path
Date: Thu, 29 Apr 2021 22:08:34 +0000
Message-ID: <20210429220839.15667-4-fllinden@amazon.com> (raw)
In-Reply-To: <20210429220839.15667-1-fllinden@amazon.com>

From: Daniel Borkmann <daniel@iogearbox.net>

commit b658bbb844e28f1862867f37e8ca11a8e2aa94a3 upstream.

Small refactor with no semantic changes in order to consolidate the max
ptr_limit boundary check.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
---
 kernel/bpf/verifier.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6cb1be115928..a6ff4b26a462 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4265,12 +4265,12 @@ static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
 
 static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
 			      const struct bpf_reg_state *off_reg,
-			      u32 *ptr_limit, u8 opcode)
+			      u32 *alu_limit, u8 opcode)
 {
 	bool off_is_neg = off_reg->smin_value < 0;
 	bool mask_to_left = (opcode == BPF_ADD &&  off_is_neg) ||
 			    (opcode == BPF_SUB && !off_is_neg);
-	u32 off, max;
+	u32 off, max = 0, ptr_limit = 0;
 
 	if (!tnum_is_const(off_reg->var_off) &&
 	    (off_reg->smin_value < 0) != (off_reg->smax_value < 0))
@@ -4287,22 +4287,27 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
 		 */
 		off = ptr_reg->off + ptr_reg->var_off.value;
 		if (mask_to_left)
-			*ptr_limit = MAX_BPF_STACK + off;
+			ptr_limit = MAX_BPF_STACK + off;
 		else
-			*ptr_limit = -off - 1;
-		return *ptr_limit >= max ? -ERANGE : 0;
+			ptr_limit = -off - 1;
+		break;
 	case PTR_TO_MAP_VALUE:
 		max = ptr_reg->map_ptr->value_size;
 		if (mask_to_left) {
-			*ptr_limit = ptr_reg->umax_value + ptr_reg->off;
+			ptr_limit = ptr_reg->umax_value + ptr_reg->off;
 		} else {
 			off = ptr_reg->smin_value + ptr_reg->off;
-			*ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
+			ptr_limit = ptr_reg->map_ptr->value_size - off - 1;
 		}
-		return *ptr_limit >= max ? -ERANGE : 0;
+		break;
 	default:
 		return -EINVAL;
 	}
+
+	if (ptr_limit >= max)
+		return -ERANGE;
+	*alu_limit = ptr_limit;
+	return 0;
 }
 
 static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,
-- 
2.23.3


  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-29 22:08 [PATCH 5.4 0/8] BPF backports for CVE-2021-29155 Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 1/8] bpf: Move off_reg into sanitize_ptr_alu Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 2/8] bpf: Ensure off_reg has no mixed signed bounds for all types Frank van der Linden
2021-04-29 22:08 ` Frank van der Linden [this message]
2021-04-29 22:08 ` [PATCH 5.4 4/8] bpf: Improve verifier error messages for users Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 5/8] bpf: Refactor and streamline bounds check into helper Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 6/8] bpf: Move sanitize_val_alu out of op switch Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 7/8] bpf: Tighten speculative pointer arithmetic mask Frank van der Linden
2021-04-29 22:08 ` [PATCH 5.4 8/8] bpf: Update selftests to reflect new error states Frank van der Linden
2021-04-30 13:38 ` [PATCH 5.4 0/8] BPF backports for CVE-2021-29155 Greg KH
2021-04-30 16:38   ` van der Linden, Frank
2021-05-01  6:05     ` Greg KH
2021-05-01 17:54       ` van der Linden, Frank
     [not found] <20210430141911.137473863@linuxfoundation.org>
2021-04-30 14:20 ` [PATCH 5.4 3/8] bpf: Rework ptr_limit into alu_limit and add common error path Greg Kroah-Hartman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210429220839.15667-4-fllinden@amazon.com \
    --to=fllinden@amazon.com \
    --cc=bpf@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

BPF Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/bpf/0 bpf/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 bpf bpf/ https://lore.kernel.org/bpf \
		bpf@vger.kernel.org
	public-inbox-index bpf

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.bpf


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git