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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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Neal Cardwell 2012-12-09 11:09:54 +00:00 committed by David S. Miller
parent f67caec906
commit 5e1f54201c
1 changed files with 24 additions and 7 deletions
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31
net/ipv4/inet_diag.c
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@ -557,6 +557,17 @@ 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;
return true;
}
static int inet_diag_bc_audit(const void *bytecode, int bytecode_len)
{
const void *bc = bytecode;
@ -572,24 +583,30 @@ 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;