coredump: plug a memory leak situation on dump_seek()

After having started writing the coredump, if filesystem reports an error
anytime while writing part of the core file, we would leak a memory page
when bailing out.

Signed-off-by: André Goddard Rosa <andre.goddard@gmail.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Roland McGrath <roland@redhat.com>
Cc: WANG Cong <amwang@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/coredump.h

@@ -16,6 +16,8 @@ static inline int dump_write(struct file *file, const void *addr, int nr)
 
 static inline int dump_seek(struct file *file, loff_t off)
 {
+	int ret = 1;
+
 	if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
 		if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
 			return 0;
@@ -29,13 +31,15 @@ static inline int dump_seek(struct file *file, loff_t off)
 
 			if (n > PAGE_SIZE)
 				n = PAGE_SIZE;
-			if (!dump_write(file, buf, n))
-				return 0;
+			if (!dump_write(file, buf, n)) {
+				ret = 0;
+				break;
+			}
 			off -= n;
 		}
 		free_page((unsigned long)buf);
 	}
-	return 1;
+	return ret;
 }
 
 #endif /* _LINUX_COREDUMP_H */