[PATCH v2] xen/privcmd: allow fetching resource sizes

Roger Pau Monne posted 1 patch 4 days, 12 hours ago
Failed in applying to current master (apply log)
drivers/xen/privcmd.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)

[PATCH v2] xen/privcmd: allow fetching resource sizes

Posted by Roger Pau Monne 4 days, 12 hours ago
Allow issuing an IOCTL_PRIVCMD_MMAP_RESOURCE ioctl with num = 0 and
addr = 0 in order to fetch the size of a specific resource.

Add a shortcut to the default map resource path, since fetching the
size requires no address to be passed in, and thus no VMA to setup.

This is missing from the initial implementation, and causes issues
when mapping resources that don't have fixed or known sizes.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: stable@vger.kernel.org # >= 4.18
---
NB: fetching the size of a resource shouldn't trigger an hypercall
preemption, and hence I've dropped the preempt indications.
---
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Paul Durrant <paul.durrant@citrix.com>
Cc: amc96@cam.ac.uk
Cc: andrew.cooper3@citrix.com
Cc: xen-devel@lists.xenproject.org
---
Changes since v1:
 - Remove Fixes tag, add backport.
 - Make sure both addr and num are set or unset.
---
 drivers/xen/privcmd.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index b0c73c58f987..720a7b7abd46 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -717,14 +717,15 @@ static long privcmd_ioctl_restrict(struct file *file, void __user *udata)
 	return 0;
 }
 
-static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
+static long privcmd_ioctl_mmap_resource(struct file *file,
+				struct privcmd_mmap_resource __user *udata)
 {
 	struct privcmd_data *data = file->private_data;
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	struct privcmd_mmap_resource kdata;
 	xen_pfn_t *pfns = NULL;
-	struct xen_mem_acquire_resource xdata;
+	struct xen_mem_acquire_resource xdata = { };
 	int rc;
 
 	if (copy_from_user(&kdata, udata, sizeof(kdata)))
@@ -734,6 +735,22 @@ static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
 	if (data->domid != DOMID_INVALID && data->domid != kdata.dom)
 		return -EPERM;
 
+	/* Both fields must be set or unset */
+	if (!!kdata.addr != !!kdata.num)
+		return -EINVAL;
+
+	xdata.domid = kdata.dom;
+	xdata.type = kdata.type;
+	xdata.id = kdata.id;
+
+	if (!kdata.addr && !kdata.num) {
+		/* Query the size of the resource. */
+		rc = HYPERVISOR_memory_op(XENMEM_acquire_resource, &xdata);
+		if (rc)
+			return rc;
+		return __put_user(xdata.nr_frames, &udata->num);
+	}
+
 	mmap_write_lock(mm);
 
 	vma = find_vma(mm, kdata.addr);
@@ -768,10 +785,6 @@ static long privcmd_ioctl_mmap_resource(struct file *file, void __user *udata)
 	} else
 		vma->vm_private_data = PRIV_VMA_LOCKED;
 
-	memset(&xdata, 0, sizeof(xdata));
-	xdata.domid = kdata.dom;
-	xdata.type = kdata.type;
-	xdata.id = kdata.id;
 	xdata.frame = kdata.idx;
 	xdata.nr_frames = kdata.num;
 	set_xen_guest_handle(xdata.frame_list, pfns);
-- 
2.29.2


Re: [PATCH v2] xen/privcmd: allow fetching resource sizes

Posted by Jürgen Groß 3 days, 12 hours ago
On 12.01.21 12:53, Roger Pau Monne wrote:
> Allow issuing an IOCTL_PRIVCMD_MMAP_RESOURCE ioctl with num = 0 and
> addr = 0 in order to fetch the size of a specific resource.
> 
> Add a shortcut to the default map resource path, since fetching the
> size requires no address to be passed in, and thus no VMA to setup.
> 
> This is missing from the initial implementation, and causes issues
> when mapping resources that don't have fixed or known sizes.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> Cc: stable@vger.kernel.org # >= 4.18

Pushed to xen/tip.git for-linus-5.11


Juergen

Re: [PATCH v2] xen/privcmd: allow fetching resource sizes

Posted by Jürgen Groß 4 days, 12 hours ago
On 12.01.21 12:53, Roger Pau Monne wrote:
> Allow issuing an IOCTL_PRIVCMD_MMAP_RESOURCE ioctl with num = 0 and
> addr = 0 in order to fetch the size of a specific resource.
> 
> Add a shortcut to the default map resource path, since fetching the
> size requires no address to be passed in, and thus no VMA to setup.
> 
> This is missing from the initial implementation, and causes issues
> when mapping resources that don't have fixed or known sizes.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> Cc: stable@vger.kernel.org # >= 4.18

Reviewed-by: Juergen Gross <jgross@suse.com>


Juergen

Re: [PATCH v2] xen/privcmd: allow fetching resource sizes

Posted by Andrew Cooper 4 days, 4 hours ago
On 12/01/2021 12:17, Jürgen Groß wrote:
> On 12.01.21 12:53, Roger Pau Monne wrote:
>> Allow issuing an IOCTL_PRIVCMD_MMAP_RESOURCE ioctl with num = 0 and
>> addr = 0 in order to fetch the size of a specific resource.
>>
>> Add a shortcut to the default map resource path, since fetching the
>> size requires no address to be passed in, and thus no VMA to setup.
>>
>> This is missing from the initial implementation, and causes issues
>> when mapping resources that don't have fixed or known sizes.
>>
>> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
>> Cc: stable@vger.kernel.org # >= 4.18
>
> Reviewed-by: Juergen Gross <jgross@suse.com>

Tested-by: Andrew Cooper <andrew.cooper3@citrix.com>