vfio: Clear the caps->buf to NULL after free

[ Upstream commit 6641085e8d7b3f061911517f79a2a15a0a21b97b ]

On buffer resize failure, vfio_info_cap_add() will free the buffer,
report zero for the size, and return -ENOMEM.  As additional
hardening, also clear the buffer pointer to prevent any chance of a
double free.

Signed-off-by: Schspa Shi <schspa@gmail.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/20220629022948.55608-1-schspa@gmail.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 388597930b648feafb04fb3a81a1b3ea43c0a749..efd3782ead9743de6fb19bcfd81c094b8a5ca6dd 100644 (file)
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1802,6 +1802,7 @@ struct vfio_info_cap_header *vfio_info_cap_add(struct vfio_info_cap *caps,
        buf = krealloc(caps->buf, caps->size + size, GFP_KERNEL);
        if (!buf) {
                kfree(caps->buf);
+               caps->buf = NULL;
                caps->size = 0;
                return ERR_PTR(-ENOMEM);
        }