netdev - [PATCH net] inet_diag: validate port comparison byte code to prevent unsafe reads

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>] [day] [month] [year] [list]

Date:	Sun,  9 Dec 2012 16:09:54 -0500
From:	Neal Cardwell <ncardwell@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	edumazet@...gle.com, netdev@...r.kernel.org,
	Neal Cardwell <ncardwell@...gle.com>
Subject: [PATCH net] inet_diag: validate port comparison byte code to prevent unsafe reads

Add logic to verify that a port comparison byte code operation
actually has the second inet_diag_bc_op from which we read the port
for such operations.

Previously the code blindly referenced op[1] without first checking
whether a second inet_diag_bc_op struct could fit there. So a
malicious user could make the kernel read 4 bytes beyond the end of
the bytecode array by claiming to have a whole port comparison byte
code (2 inet_diag_bc_op structs) when in fact the bytecode was not
long enough to hold both.

Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
---
[Patch was generated relative to the previous 3-patch inet_diag patch series
 from last night.]
 net/ipv4/inet_diag.c |   30 +++++++++++++++++++++++-------
 1 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 95f1a45..67746f5 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -557,6 +557,16 @@ static bool valid_hostcond(const struct inet_diag_bc_op *op, int len,
 	return true;
 }
 
+/* Validate a port comparison operator. */
+static inline bool valid_port_comparison(const struct inet_diag_bc_op *op,
+					 int len, int *min_len)
+{
+	/* Port comparisons put the port in a follow-on inet_diag_bc_op. */
+	*min_len += sizeof(struct inet_diag_bc_op);
+	if (len < *min_len)
+		return false;
+}
+
 static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
 {
 	const void *bc = bytecode;
@@ -572,24 +582,30 @@ static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
 		case INET_DIAG_BC_D_COND:
 			if (!valid_hostcond(bc, len, &min_len))
 				return -EINVAL;
-			/* fall through */
-		case INET_DIAG_BC_AUTO:
+			break;
 		case INET_DIAG_BC_S_GE:
 		case INET_DIAG_BC_S_LE:
 		case INET_DIAG_BC_D_GE:
 		case INET_DIAG_BC_D_LE:
-		case INET_DIAG_BC_JMP:
-			if (op->no < min_len || op->no > len + 4 || op->no & 3)
-				return -EINVAL;
-			if (op->no < len &&
-			    !valid_cc(bytecode, bytecode_len, len - op->no))
+			if (!valid_port_comparison(bc, len, &min_len))
 				return -EINVAL;
 			break;
+		case INET_DIAG_BC_AUTO:
+		case INET_DIAG_BC_JMP:
 		case INET_DIAG_BC_NOP:
 			break;
 		default:
 			return -EINVAL;
 		}
+
+		if (op->code != INET_DIAG_BC_NOP) {
+			if (op->no < min_len || op->no > len + 4 || op->no & 3)
+				return -EINVAL;
+			if (op->no < len &&
+			    !valid_cc(bytecode, bytecode_len, len - op->no))
+				return -EINVAL;
+		}
+
 		if (op->yes < min_len || op->yes > len + 4 || op->yes & 3)
 			return -EINVAL;
 		bc  += op->yes;
-- 
1.7.7.3

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html