mm/nommu.c: add additional check for vread() just like vwrite() has done

vwrite() checks for overflow. vread() should do the same thing.

Since vwrite() checks the source buffer address, vread() should check
the destination buffer address.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/nommu.c b/mm/nommu.c
index 886e07ce4d1decbba6a3eafd3a104a1d1d3a9257..0614ee1eeb664e26549a858a7d1e2739f93f526e 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -282,6 +282,10 @@ EXPORT_SYMBOL(vmalloc_to_pfn);
 
 long vread(char *buf, char *addr, unsigned long count)
 {
+       /* Don't allow overflow */
+       if ((unsigned long) buf + count < count)
+               count = -(unsigned long) buf;
+
        memcpy(buf, addr, count);
        return count;
 }