alpha: Prevent a NULL ptr dereference in csum_partial_copy.

Introduced by 3ddc5b46a8e90f3c92 ("kernel-wide: fix missing validations
on __get/__put/__copy_to/__copy_from_user()").

Also fix some other places which could be problematic in a similar way,
although they hadn't been proved so, as far as I can tell.

Cc: Michael Cree <mcree@orcon.net.nz>
Signed-off-by: Matt Turner <mattst88@gmail.com>

diff --git a/arch/alpha/lib/csum_partial_copy.c b/arch/alpha/lib/csum_partial_copy.c
index ffb19b7da999c67722d5690dcfcd6ef0d74123f8..ff3c10721caf67be1873f5c5b88623fc65fd89ea 100644 (file)
--- a/arch/alpha/lib/csum_partial_copy.c
+++ b/arch/alpha/lib/csum_partial_copy.c
@@ -130,7 +130,7 @@ csum_partial_cfu_aligned(const unsigned long __user *src, unsigned long *dst,
                *dst = word | tmp;
                checksum += carry;
        }
-       if (err) *errp = err;
+       if (err && errp) *errp = err;
        return checksum;
 }
 
@@ -185,7 +185,7 @@ csum_partial_cfu_dest_aligned(const unsigned long __user *src,
                *dst = word | tmp;
                checksum += carry;
        }
-       if (err) *errp = err;
+       if (err && errp) *errp = err;
        return checksum;
 }
 
@@ -242,7 +242,7 @@ csum_partial_cfu_src_aligned(const unsigned long __user *src,
        stq_u(partial_dest | second_dest, dst);
 out:
        checksum += carry;
-       if (err) *errp = err;
+       if (err && errp) *errp = err;
        return checksum;
 }
 
@@ -325,7 +325,7 @@ csum_partial_cfu_unaligned(const unsigned long __user * src,
                stq_u(partial_dest | word | second_dest, dst);
                checksum += carry;
        }
-       if (err) *errp = err;
+       if (err && errp) *errp = err;
        return checksum;
 }
 
@@ -339,7 +339,7 @@ csum_partial_copy_from_user(const void __user *src, void *dst, int len,
 
        if (len) {
                if (!access_ok(VERIFY_READ, src, len)) {
-                       *errp = -EFAULT;
+                       if (errp) *errp = -EFAULT;
                        memset(dst, 0, len);
                        return sum;
                }