From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Thu, 4 Apr 2019 15:12:17 +0000 (+0300)
Subject: xen: Prevent buffer overflow in privcmd ioctl
X-Git-Tag: v3.18.139~51
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cfa402909d9cf80d6526f2d54b39c3b8cbd5fff5;p=thirdparty%2Fkernel%2Fstable.git

xen: Prevent buffer overflow in privcmd ioctl

commit 42d8644bd77dd2d747e004e367cb0c895a606f39 upstream.

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: stable@vger.kernel.org
Fixes: 1246ae0bb992 ("xen: add variable hypercall caller")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index ca08a27b90b3d..6e1e86781d90e 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -213,6 +213,9 @@ privcmd_call(unsigned call,
 	__HYPERCALL_DECLS;
 	__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
 
+	if (call >= PAGE_SIZE / sizeof(hypercall_page[0]))
+		return -EINVAL;
+
 	asm volatile("call *%[call]"
 		     : __HYPERCALL_5PARAM
 		     : [call] "a" (&hypercall_page[call])