net: Add explicit bound checks in net/socket.c

The sys_socketcall() function has a very clever system for the copy
size of its arguments. Unfortunately, gcc cannot deal with this in
terms of proving that the copy_from_user() is then always in bounds.
This is the last (well 9th of this series, but last in the kernel) such
case around.

With this patch, we can turn on code to make having the boundary provably
right for the whole kernel, and detect introduction of new security
accidents of this type early on.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/socket.c b/net/socket.c
index 49917a1cac7d921f6fae418bb89a19a4e9e02a1f..41e8847508aad85a22f1ba61e4999daa5ca46342 100644 (file)
--- a/net/socket.c
+++ b/net/socket.c
@@ -2098,12 +2098,17 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
        unsigned long a[6];
        unsigned long a0, a1;
        int err;
+       unsigned int len;
 
        if (call < 1 || call > SYS_ACCEPT4)
                return -EINVAL;
 
+       len = nargs[call];
+       if (len > sizeof(a))
+               return -EINVAL;
+
        /* copy_from_user should be SMP safe. */
-       if (copy_from_user(a, args, nargs[call]))
+       if (copy_from_user(a, args, len))
                return -EFAULT;
 
        audit_socketcall(nargs[call] / sizeof(unsigned long), a);