As 'be->blkif' is used for many times in connect_ring(), the stack variable
'blkif' is added to substitute 'be-blkif'.
Suggested-by: Paul Durrant <[email protected]>
Signed-off-by: Dongli Zhang <[email protected]>
Reviewed-by: Paul Durrant <[email protected]>
Reviewed-by: Roger Pau Monné <[email protected]>
---
drivers/block/xen-blkback/xenbus.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index a4bc74e..a4aadac 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -1023,6 +1023,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
static int connect_ring(struct backend_info *be)
{
struct xenbus_device *dev = be->dev;
+ struct xen_blkif *blkif = be->blkif;
unsigned int pers_grants;
char protocol[64] = "";
int err, i;
@@ -1033,25 +1034,25 @@ static int connect_ring(struct backend_info *be)
pr_debug("%s %s\n", __func__, dev->otherend);
- be->blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
+ blkif->blk_protocol = BLKIF_PROTOCOL_DEFAULT;
err = xenbus_scanf(XBT_NIL, dev->otherend, "protocol",
"%63s", protocol);
if (err <= 0)
strcpy(protocol, "unspecified, assuming default");
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_NATIVE))
- be->blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
+ blkif->blk_protocol = BLKIF_PROTOCOL_NATIVE;
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_32))
- be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
+ blkif->blk_protocol = BLKIF_PROTOCOL_X86_32;
else if (0 == strcmp(protocol, XEN_IO_PROTO_ABI_X86_64))
- be->blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
+ blkif->blk_protocol = BLKIF_PROTOCOL_X86_64;
else {
xenbus_dev_fatal(dev, err, "unknown fe protocol %s", protocol);
return -ENOSYS;
}
pers_grants = xenbus_read_unsigned(dev->otherend, "feature-persistent",
0);
- be->blkif->vbd.feature_gnt_persistent = pers_grants;
- be->blkif->vbd.overflow_max_grants = 0;
+ blkif->vbd.feature_gnt_persistent = pers_grants;
+ blkif->vbd.overflow_max_grants = 0;
/*
* Read the number of hardware queues from frontend.
@@ -1067,16 +1068,16 @@ static int connect_ring(struct backend_info *be)
requested_num_queues, xenblk_max_queues);
return -ENOSYS;
}
- be->blkif->nr_rings = requested_num_queues;
- if (xen_blkif_alloc_rings(be->blkif))
+ blkif->nr_rings = requested_num_queues;
+ if (xen_blkif_alloc_rings(blkif))
return -ENOMEM;
pr_info("%s: using %d queues, protocol %d (%s) %s\n", dev->nodename,
- be->blkif->nr_rings, be->blkif->blk_protocol, protocol,
+ blkif->nr_rings, blkif->blk_protocol, protocol,
pers_grants ? "persistent grants" : "");
- if (be->blkif->nr_rings == 1)
- return read_per_ring_refs(&be->blkif->rings[0], dev->otherend);
+ if (blkif->nr_rings == 1)
+ return read_per_ring_refs(&blkif->rings[0], dev->otherend);
else {
xspathsize = strlen(dev->otherend) + xenstore_path_ext_size;
xspath = kmalloc(xspathsize, GFP_KERNEL);
@@ -1085,10 +1086,10 @@ static int connect_ring(struct backend_info *be)
return -ENOMEM;
}
- for (i = 0; i < be->blkif->nr_rings; i++) {
+ for (i = 0; i < blkif->nr_rings; i++) {
memset(xspath, 0, xspathsize);
snprintf(xspath, xspathsize, "%s/queue-%u", dev->otherend, i);
- err = read_per_ring_refs(&be->blkif->rings[i], xspath);
+ err = read_per_ring_refs(&blkif->rings[i], xspath);
if (err) {
kfree(xspath);
return err;
--
2.7.4
The xenstore 'ring-page-order' is used globally for each blkback queue and
therefore should be read from xenstore only once. However, it is obtained
in read_per_ring_refs() which might be called multiple times during the
initialization of each blkback queue.
If the blkfront is malicious and the 'ring-page-order' is set in different
value by blkfront every time before blkback reads it, this may end up at
the "WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));" in
xen_blkif_disconnect() when frontend is destroyed.
This patch reworks connect_ring() to read xenstore 'ring-page-order' only
once.
Signed-off-by: Dongli Zhang <[email protected]>
---
Changed since v1:
* change the order of xenstore read in read_per_ring_refs
* use xenbus_read_unsigned() in connect_ring()
Changed since v2:
* simplify the condition check as "(err != 1 && nr_grefs > 1)"
* avoid setting err as -EINVAL to remove extra one line of code
Changed since v3:
* exit at the beginning if !nr_grefs
* change the if statements to avoid test (err != 1) twice
* initialize a 'blkif' stack variable (refer to PATCH 1/2)
Changed since v4:
* use BUG_ON() when (nr_grefs == 0) to reminder the developer
* set err = -EINVAL before xenbus_dev_fatal()
drivers/block/xen-blkback/xenbus.c | 69 ++++++++++++++++++++++----------------
1 file changed, 40 insertions(+), 29 deletions(-)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index a4aadac..f6146cd 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -926,7 +926,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
int err, i, j;
struct xen_blkif *blkif = ring->blkif;
struct xenbus_device *dev = blkif->be->dev;
- unsigned int ring_page_order, nr_grefs, evtchn;
+ unsigned int nr_grefs, evtchn;
err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
&evtchn);
@@ -936,43 +936,39 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
return err;
}
- err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
- &ring_page_order);
- if (err != 1) {
- err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
+ nr_grefs = blkif->nr_ring_pages;
+
+ BUG_ON(!nr_grefs);
+
+ for (i = 0; i < nr_grefs; i++) {
+ char ring_ref_name[RINGREF_NAME_LEN];
+
+ snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
+ err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
+ "%u", &ring_ref[i]);
+
if (err != 1) {
+ if (nr_grefs == 1)
+ break;
+
err = -EINVAL;
- xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
+ xenbus_dev_fatal(dev, err, "reading %s/%s",
+ dir, ring_ref_name);
return err;
}
- nr_grefs = 1;
- } else {
- unsigned int i;
+ }
- if (ring_page_order > xen_blkif_max_ring_order) {
+ if (err != 1) {
+ WARN_ON(nr_grefs != 1);
+
+ err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u",
+ &ring_ref[0]);
+ if (err != 1) {
err = -EINVAL;
- xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
- dir, ring_page_order,
- xen_blkif_max_ring_order);
+ xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
return err;
}
-
- nr_grefs = 1 << ring_page_order;
- for (i = 0; i < nr_grefs; i++) {
- char ring_ref_name[RINGREF_NAME_LEN];
-
- snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
- err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
- "%u", &ring_ref[i]);
- if (err != 1) {
- err = -EINVAL;
- xenbus_dev_fatal(dev, err, "reading %s/%s",
- dir, ring_ref_name);
- return err;
- }
- }
}
- blkif->nr_ring_pages = nr_grefs;
for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
req = kzalloc(sizeof(*req), GFP_KERNEL);
@@ -1031,6 +1027,7 @@ static int connect_ring(struct backend_info *be)
size_t xspathsize;
const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
unsigned int requested_num_queues = 0;
+ unsigned int ring_page_order;
pr_debug("%s %s\n", __func__, dev->otherend);
@@ -1076,6 +1073,20 @@ static int connect_ring(struct backend_info *be)
blkif->nr_rings, blkif->blk_protocol, protocol,
pers_grants ? "persistent grants" : "");
+ ring_page_order = xenbus_read_unsigned(dev->otherend,
+ "ring-page-order", 0);
+
+ if (ring_page_order > xen_blkif_max_ring_order) {
+ err = -EINVAL;
+ xenbus_dev_fatal(dev, err,
+ "requested ring page order %d exceed max:%d",
+ ring_page_order,
+ xen_blkif_max_ring_order);
+ return err;
+ }
+
+ blkif->nr_ring_pages = 1 << ring_page_order;
+
if (blkif->nr_rings == 1)
return read_per_ring_refs(&blkif->rings[0], dev->otherend);
else {
--
2.7.4
oops. Please ignore this v5 patch.
I just realized Linus suggested in an old email not use BUG()/BUG_ON() in the code.
I will switch to the WARN() solution and resend again.
Sorry for the junk email.
Dongli Zhang
On 2019/1/8 下午4:15, Dongli Zhang wrote:
> The xenstore 'ring-page-order' is used globally for each blkback queue and
> therefore should be read from xenstore only once. However, it is obtained
> in read_per_ring_refs() which might be called multiple times during the
> initialization of each blkback queue.
>
> If the blkfront is malicious and the 'ring-page-order' is set in different
> value by blkfront every time before blkback reads it, this may end up at
> the "WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));" in
> xen_blkif_disconnect() when frontend is destroyed.
>
> This patch reworks connect_ring() to read xenstore 'ring-page-order' only
> once.
>
> Signed-off-by: Dongli Zhang <[email protected]>
> ---
> Changed since v1:
> * change the order of xenstore read in read_per_ring_refs
> * use xenbus_read_unsigned() in connect_ring()
>
> Changed since v2:
> * simplify the condition check as "(err != 1 && nr_grefs > 1)"
> * avoid setting err as -EINVAL to remove extra one line of code
>
> Changed since v3:
> * exit at the beginning if !nr_grefs
> * change the if statements to avoid test (err != 1) twice
> * initialize a 'blkif' stack variable (refer to PATCH 1/2)
>
> Changed since v4:
> * use BUG_ON() when (nr_grefs == 0) to reminder the developer
> * set err = -EINVAL before xenbus_dev_fatal()
>
> drivers/block/xen-blkback/xenbus.c | 69 ++++++++++++++++++++++----------------
> 1 file changed, 40 insertions(+), 29 deletions(-)
>
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index a4aadac..f6146cd 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -926,7 +926,7 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
> int err, i, j;
> struct xen_blkif *blkif = ring->blkif;
> struct xenbus_device *dev = blkif->be->dev;
> - unsigned int ring_page_order, nr_grefs, evtchn;
> + unsigned int nr_grefs, evtchn;
>
> err = xenbus_scanf(XBT_NIL, dir, "event-channel", "%u",
> &evtchn);
> @@ -936,43 +936,39 @@ static int read_per_ring_refs(struct xen_blkif_ring *ring, const char *dir)
> return err;
> }
>
> - err = xenbus_scanf(XBT_NIL, dev->otherend, "ring-page-order", "%u",
> - &ring_page_order);
> - if (err != 1) {
> - err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u", &ring_ref[0]);
> + nr_grefs = blkif->nr_ring_pages;
> +
> + BUG_ON(!nr_grefs);
> +
> + for (i = 0; i < nr_grefs; i++) {
> + char ring_ref_name[RINGREF_NAME_LEN];
> +
> + snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
> + err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
> + "%u", &ring_ref[i]);
> +
> if (err != 1) {
> + if (nr_grefs == 1)
> + break;
> +
> err = -EINVAL;
> - xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
> + xenbus_dev_fatal(dev, err, "reading %s/%s",
> + dir, ring_ref_name);
> return err;
> }
> - nr_grefs = 1;
> - } else {
> - unsigned int i;
> + }
>
> - if (ring_page_order > xen_blkif_max_ring_order) {
> + if (err != 1) {
> + WARN_ON(nr_grefs != 1);
> +
> + err = xenbus_scanf(XBT_NIL, dir, "ring-ref", "%u",
> + &ring_ref[0]);
> + if (err != 1) {
> err = -EINVAL;
> - xenbus_dev_fatal(dev, err, "%s/request %d ring page order exceed max:%d",
> - dir, ring_page_order,
> - xen_blkif_max_ring_order);
> + xenbus_dev_fatal(dev, err, "reading %s/ring-ref", dir);
> return err;
> }
> -
> - nr_grefs = 1 << ring_page_order;
> - for (i = 0; i < nr_grefs; i++) {
> - char ring_ref_name[RINGREF_NAME_LEN];
> -
> - snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
> - err = xenbus_scanf(XBT_NIL, dir, ring_ref_name,
> - "%u", &ring_ref[i]);
> - if (err != 1) {
> - err = -EINVAL;
> - xenbus_dev_fatal(dev, err, "reading %s/%s",
> - dir, ring_ref_name);
> - return err;
> - }
> - }
> }
> - blkif->nr_ring_pages = nr_grefs;
>
> for (i = 0; i < nr_grefs * XEN_BLKIF_REQS_PER_PAGE; i++) {
> req = kzalloc(sizeof(*req), GFP_KERNEL);
> @@ -1031,6 +1027,7 @@ static int connect_ring(struct backend_info *be)
> size_t xspathsize;
> const size_t xenstore_path_ext_size = 11; /* sufficient for "/queue-NNN" */
> unsigned int requested_num_queues = 0;
> + unsigned int ring_page_order;
>
> pr_debug("%s %s\n", __func__, dev->otherend);
>
> @@ -1076,6 +1073,20 @@ static int connect_ring(struct backend_info *be)
> blkif->nr_rings, blkif->blk_protocol, protocol,
> pers_grants ? "persistent grants" : "");
>
> + ring_page_order = xenbus_read_unsigned(dev->otherend,
> + "ring-page-order", 0);
> +
> + if (ring_page_order > xen_blkif_max_ring_order) {
> + err = -EINVAL;
> + xenbus_dev_fatal(dev, err,
> + "requested ring page order %d exceed max:%d",
> + ring_page_order,
> + xen_blkif_max_ring_order);
> + return err;
> + }
> +
> + blkif->nr_ring_pages = 1 << ring_page_order;
> +
> if (blkif->nr_rings == 1)
> return read_per_ring_refs(&blkif->rings[0], dev->otherend);
> else {
>
On 2019/1/17 上午12:32, Konrad Rzeszutek Wilk wrote:
> On Tue, Jan 08, 2019 at 04:24:32PM +0800, Dongli Zhang wrote:
>> oops. Please ignore this v5 patch.
>>
>> I just realized Linus suggested in an old email not use BUG()/BUG_ON() in the code.
>>
>> I will switch to the WARN() solution and resend again.
>
> OK. Did I miss it?
Hi Konrad,
If you are talking about the new patch set:
https://lists.xenproject.org/archives/html/xen-devel/2019-01/msg00977.html
https://lists.xenproject.org/archives/html/xen-devel/2019-01/msg00978.html
About Linus' suggestion:
http://lkml.iu.edu/hypermail/linux/kernel/1610.0/00878.html
Dongli Zhang
>
> _______________________________________________
> Xen-devel mailing list
> [email protected]
> https://lists.xenproject.org/mailman/listinfo/xen-devel
>
On Tue, Jan 08, 2019 at 04:24:32PM +0800, Dongli Zhang wrote:
> oops. Please ignore this v5 patch.
>
> I just realized Linus suggested in an old email not use BUG()/BUG_ON() in the code.
>
> I will switch to the WARN() solution and resend again.
OK. Did I miss it?