[ 12/80] inet_diag: validate port comparison byte code to prevent unsafe reads

Greg Kroah-Hartman
2013-01-09T20:37:38Z

From: Neal Cardwell <ncardwell@google.com>

[ Upstream commit 5e1f54201cb481f40a04bc47e1bc8c093a189e23 ]

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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/inet_diag.c | 31 ++++++++++++++++++++++++-------
1 file changed, 24 insertions(+), 7 deletions(-)

--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -548,6 +548,17 @@ static bool valid_hostcond(const struct
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;
+ return true;
+}
+
static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
{
const void *bc = bytecode;
@@ -563,24 +574,30 @@ static int inet_diag_bc_audit(const void
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;