linux-kernel - [RFC 1/8] vfio: fix vfio_info_cap

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Date:   Thu,  3 Nov 2016 21:39:31 +0000
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger@...hat.com, eric.auger.pro@...il.com,
        christoffer.dall@...aro.org, marc.zyngier@....com,
        robin.murphy@....com, alex.williamson@...hat.com,
        will.deacon@....com, joro@...tes.org, tglx@...utronix.de,
        jason@...edaemon.net, linux-arm-kernel@...ts.infradead.org
Cc:     kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, pranav.sawargaonkar@...il.com,
        iommu@...ts.linux-foundation.org, punit.agrawal@....com,
        diana.craciun@....com
Subject: [RFC 1/8] vfio: fix vfio_info_cap_add/shift

Capability header next field is an offset relative to the start of
the INFO buffer. tmp->next is assigned the proper value but iterations
implemented in vfio_info_cap_add and vfio_info_cap_shift use next
as an offset between the headers. When coping with multiple capabilities
this leads to an Oops.

Signed-off-by: Eric Auger <eric.auger@...hat.com>
---
 drivers/vfio/vfio.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index d1d70e0..1e838d1 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1763,7 +1763,7 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
 	header->version = version;
 
 	/* Add to the end of the capability chain */
-	for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next)
+	for (tmp = buf; tmp->next; tmp = buf + tmp->next)
 		; /* nothing */
 
 	tmp->next = caps->size;
@@ -1776,8 +1776,9 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
 void vfio_info_cap_shift(struct vfio_info_cap *caps, size_t offset)
 {
 	struct vfio_info_cap_header *tmp;
+	void *buf = (void *)caps->buf;
 
-	for (tmp = caps->buf; tmp->next; tmp = (void *)tmp + tmp->next - offset)
+	for (tmp = buf; tmp->next; tmp = buf + tmp->next - offset)
 		tmp->next += offset;
 }
 EXPORT_SYMBOL_GPL(vfio_info_cap_shift);
-- 
1.9.1