xen: Prevent buffer overflow in privcmd ioctl

The "call" variable comes from the user in privcmd_ioctl_hypercall(). It's an offset into the hypercall_page[] which has (PAGE_SIZE / 32) elements. We need to put an upper bound on it to prevent an out of bounds access. Cc: [email protected] Fixes: 1246ae0 ("xen: add variable hypercall caller") Signed-off-by: Dan Carpenter <[email protected]> Reviewed-by: Boris Ostrovsky <[email protected]> Signed-off-by: Juergen Gross <[email protected]>
mrcsosa · Apr 5, 2019 · 42d8644 · 42d8644
1 parent ad94dc3
commit 42d8644
Showing 1 changed file with 3 additions and 0 deletions.
diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
@@ -206,6 +206,9 @@ xen_single_call(unsigned int call,
 	__HYPERCALL_DECLS;
 	__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
 
+	if (call >= PAGE_SIZE / sizeof(hypercall_page[0]))
+		return -EINVAL;
+
 	asm volatile(CALL_NOSPEC
 		     : __HYPERCALL_5PARAM
 		     : [thunk_target] "a" (&hypercall_page[call])