xen/gntalloc: Replace UAPI 1-element array

Without changing the structure size (since it is UAPI), add a proper
flexible array member, and reference it in the kernel so that it will
not be trip the array-bounds sanitizer[1].

Link: https://github.com/KSPP/linux/issues/113
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Gustavo A. R. Silva <gustavoars@kernel.org>
Cc: xen-devel@lists.xenproject.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20240206170320.work.437-kees@kernel.org
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
index 26ffb8755ffb5da27bd1eb38ceeb59ca06c473ed..f93f73ecefeee4b2b052a3ac758a8fbf9fdc11ae 100644 (file)
--- a/drivers/xen/gntalloc.c
+++ b/drivers/xen/gntalloc.c
@@ -317,7 +317,7 @@ static long gntalloc_ioctl_alloc(struct gntalloc_file_private_data *priv,
                rc = -EFAULT;
                goto out_free;
        }
-       if (copy_to_user(arg->gref_ids, gref_ids,
+       if (copy_to_user(arg->gref_ids_flex, gref_ids,
                        sizeof(gref_ids[0]) * op.count)) {
                rc = -EFAULT;
                goto out_free;

diff --git a/include/uapi/xen/gntalloc.h b/include/uapi/xen/gntalloc.h
index 48d2790ef928c798279babb69fbd07f7d6dcc20d..3109282672f33cecc00cd3f08e9dfd22e7991637 100644 (file)
--- a/include/uapi/xen/gntalloc.h
+++ b/include/uapi/xen/gntalloc.h
@@ -31,7 +31,10 @@ struct ioctl_gntalloc_alloc_gref {
        __u64 index;
        /* The grant references of the newly created grant, one per page */
        /* Variable size, depending on count */
-       __u32 gref_ids[1];
+       union {
+               __u32 gref_ids[1];
+               __DECLARE_FLEX_ARRAY(__u32, gref_ids_flex);
+       };
 };
 
 #define GNTALLOC_FLAG_WRITABLE 1