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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 04/17] bpf: Rework ptr_limit into alu_limit and add common error path
Date: Mon, 31 May 2021 18:25:43 +0000	[thread overview]
Message-ID: <20210531182556.25277-5-fllinden@amazon.com> (raw)
In-Reply-To: <20210531182556.25277-1-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 9cb2c035f06d..12cb6b1c4e9b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2026,12 +2026,12 @@ 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))
@@ -2045,22 +2045,27 @@ static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
 		max = MAX_BPF_STACK + mask_to_left;
 		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,
-- 
2.23.4


  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 ` Frank van der Linden [this message]
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 ` [PATCH v2 4.14 11/17] bpf/verifier: disallow pointer subtraction Frank van der Linden
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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