fuse: verify all ioctl retry iov elements

commit fb6ccff667712c46b4501b920ea73a326e49626a upstream.

Commit 7572777eef78ebdee1ecb7c258c0ef94d35bad16 attempted to verify that
the total iovec from the client doesn't overflow iov_length() but it
only checked the first element.  The iovec could still overflow by
starting with a small element.  The obvious fix is to check all the
elements.

The overflow case doesn't look dangerous to the kernel as the copy is
limited by the length after the overflow.  This fix restores the
intention of returning an error instead of successfully copying less
than the iovec represented.

I found this by code inspection.  I built it but don't have a test case.
I'm cc:ing stable because the initial commit did as well.

Signed-off-by: Zach Brown <zab@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 504e61b7fd7515f8aafe7e3b9edd2c9fa42fd91d..8e6381a14265025764c69d183f17ef7446939d3d 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1698,7 +1698,7 @@ static int fuse_verify_ioctl_iov(struct iovec *iov, size_t count)
        size_t n;
        u32 max = FUSE_MAX_PAGES_PER_REQ << PAGE_SHIFT;
 
-       for (n = 0; n < count; n++) {
+       for (n = 0; n < count; n++, iov++) {
                if (iov->iov_len > (size_t) max)
                        return -ENOMEM;
                max -= iov->iov_len;