1 files changed, 44 insertions, 6 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9242d294fe90..0e2e25b114a6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -13,6 +13,7 @@
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/module.h>
+#include <linux/compat.h>
 
 static const struct file_operations fuse_direct_io_file_operations;
 
@@ -1628,6 +1629,44 @@ static int fuse_ioctl_copy_user(struct page **pages, struct iovec *iov,
 }
 
 /*
+ * CUSE servers compiled on 32bit broke on 64bit kernels because the
+ * ABI was defined to be 'struct iovec' which is different on 32bit
+ * and 64bit.  Fortunately we can determine which structure the server
+ * used from the size of the reply.
+ */
+static int fuse_copy_ioctl_iovec(struct iovec *dst, void *src,
+                                 size_t transferred, unsigned count,
+                                 bool is_compat)
+{
+#ifdef CONFIG_COMPAT
+        if (count * sizeof(struct compat_iovec) == transferred) {
+                struct compat_iovec *ciov = src;
+                unsigned i;
+
+                /*
+                 * With this interface a 32bit server cannot support
+                 * non-compat (i.e. ones coming from 64bit apps) ioctl
+                 * requests
+                 */
+                if (!is_compat)
+                        return -EINVAL;
+
+                for (i = 0; i < count; i++) {
+                        dst[i].iov_base = compat_ptr(ciov[i].iov_base);
+                        dst[i].iov_len = ciov[i].iov_len;
+                }
+                return 0;
+        }
+#endif
+
+        if (count * sizeof(struct iovec) != transferred)
+                return -EIO;
+
+        memcpy(dst, src, transferred);
+        return 0;
+}
+
+/*
  * For ioctls, there is no generic way to determine how much memory
  * needs to be read and/or written.  Furthermore, ioctls are allowed
  * to dereference the passed pointer, so the parameter requires deep
@@ -1808,14 +1847,13 @@ long fuse_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg,
                     in_iovs + out_iovs > FUSE_IOCTL_MAX_IOV)
                         goto out;
 
-                err = -EIO;
-                if ((in_iovs + out_iovs) * sizeof(struct iovec) != transferred)
-                        goto out;
-
-                /* okay, copy in iovs and retry */
                 vaddr = kmap_atomic(pages[0], KM_USER0);
-                memcpy(page_address(iov_page), vaddr, transferred);
+                err = fuse_copy_ioctl_iovec(page_address(iov_page), vaddr,
+                                            transferred, in_iovs + out_iovs,
+                                            (flags & FUSE_IOCTL_COMPAT) != 0);
                 kunmap_atomic(vaddr, KM_USER0);
+                if (err)
+                        goto out;
 
                 in_iov = page_address(iov_page);
                 out_iov = in_iov + in_iovs;