From: Wentao Liang Date: Mon, 22 Jun 2026 11:25:41 +0000 (+0800) Subject: xen/gntdev: fix error handling in ioctl X-Git-Tag: v7.2-rc2~16^2~5 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=45ca1afe2fd14c04e37227e79d3f8455831d8408;p=thirdparty%2Fkernel%2Flinux.git xen/gntdev: fix error handling in ioctl When gntdev_ioctl_map_grant_ref() fails to copy the operation result back to userspace after successfully adding the mapping to the list, the error path returns -EFAULT without releasing the reference acquired by gntdev_alloc_map(). The mapping remains in priv->maps with a refcount of 1, causing a memory leak and a dangling list entry. Additionally, gntdev_add_map() may modify map->index to avoid overlap with existing mappings. Therefore, the index returned to userspace must be obtained after gntdev_add_map() completes. Fix this by holding the mutex across gntdev_add_map(), retrieving the correct index, and copy_to_user(). If copy_to_user() fails, remove the mapping from the list and release the reference while still holding the lock. Cc: stable@vger.kernel.org Fix these issues by properly handling all error cases. Fixes: 1401c00e59ea ("xen/gntdev: convert priv->lock to a mutex") Fixes: 68b025c813c2 ("xen-gntdev: Add reference counting to maps") Signed-off-by: Wentao Liang Reviewed-by: Juergen Gross Signed-off-by: Juergen Gross Message-ID: <20260622112541.38194-1-vulab@iscas.ac.cn> --- diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c index 61ea855c4508..1dcc4675580e 100644 --- a/drivers/xen/gntdev.c +++ b/drivers/xen/gntdev.c @@ -670,11 +670,15 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv, mutex_lock(&priv->lock); gntdev_add_map(priv, map); op.index = map->index << PAGE_SHIFT; - mutex_unlock(&priv->lock); - if (copy_to_user(u, &op, sizeof(op)) != 0) + if (copy_to_user(u, &op, sizeof(op)) != 0) { + list_del(&map->next); + mutex_unlock(&priv->lock); + gntdev_put_map(priv, map); return -EFAULT; + } + mutex_unlock(&priv->lock); return 0; }