linux-kernel - [PATCH 4.19 04/28] xen/privcmd: fix error handling in mmap-resource processing

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Message-Id: <20211011134640.856296875@linuxfoundation.org>
Date:   Mon, 11 Oct 2021 15:46:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jan Beulich <jbeulich@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>
Subject: [PATCH 4.19 04/28] xen/privcmd: fix error handling in mmap-resource processing

From: Jan Beulich <jbeulich@...e.com>

commit e11423d6721dd63b23fb41ade5e8d0b448b17780 upstream.

xen_pfn_t is the same size as int only on 32-bit builds (and not even
on Arm32). Hence pfns[] can't be used directly to read individual error
values returned from xen_remap_domain_mfn_array(); every other error
indicator would be skipped/ignored on 64-bit.

Fixes: 3ad0876554ca ("xen/privcmd: add IOCTL_PRIVCMD_MMAP_RESOURCE")
Cc: stable@...r.kernel.org
Signed-off-by: Jan Beulich <jbeulich@...e.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

Link: https://lore.kernel.org/r/aa6d6a67-6889-338a-a910-51e889f792d5@suse.com
Signed-off-by: Juergen Gross <jgross@...e.com>
---
 drivers/xen/privcmd.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -835,11 +835,12 @@ static long privcmd_ioctl_mmap_resource(
 		unsigned int domid =
 			(xdata.flags & XENMEM_rsrc_acq_caller_owned) ?
 			DOMID_SELF : kdata.dom;
-		int num;
+		int num, *errs = (int *)pfns;
 
+		BUILD_BUG_ON(sizeof(*errs) > sizeof(*pfns));
 		num = xen_remap_domain_mfn_array(vma,
 						 kdata.addr & PAGE_MASK,
-						 pfns, kdata.num, (int *)pfns,
+						 pfns, kdata.num, errs,
 						 vma->vm_page_prot,
 						 domid,
 						 vma->vm_private_data);
@@ -849,7 +850,7 @@ static long privcmd_ioctl_mmap_resource(
 			unsigned int i;
 
 			for (i = 0; i < num; i++) {
-				rc = pfns[i];
+				rc = errs[i];
 				if (rc < 0)
 					break;
 			}