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scsi: storvsc: Use struct_size() helper in storvsc_queuecommand()

PATCH In review Gustavo A. R. Silva 2 participants 2 messages Jan 25, 2022 – Jan 27, 2022

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SCSI Hyper-V/Azure core and drivers Microsoft MANA RDMA driver
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Gustavo A. R. Silva

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#0 lore raw

PATCH 1/1 scsi: storvsc: Use struct_size() helper in storvsc_queuecommand()

Make use of the struct_size() helper instead of an open-coded version, in order to avoid any potential type mistakes or integer overflows that, in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
drivers/scsi/storvsc_drv.c:1843:39: warning: using sizeof on a flexible structure

Link https://github.com/KSPP/linux/issues/174
Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 drivers/scsi/storvsc_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
drivers/scsi/storvsc_drv.c +3 -3
index 9a0bba5a51a7..89c20dfc6609 100644
@@ -1755,7 +1755,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 	struct scatterlist *sgl;
 	struct vmscsi_request *vm_srb;
 	struct vmbus_packet_mpb_array  *payload;
-	u32 payload_sz;
+	size_t payload_sz;
 	u32 length;
 
 	if (vmstor_proto_version <= VMSTOR_PROTO_VERSION_WIN8) {

@@ -1839,8 +1839,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 
 		if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
 
-			payload_sz = (hvpg_count * sizeof(u64) +
-				      sizeof(struct vmbus_packet_mpb_array));
+			payload_sz = struct_size(payload, range.pfn_array,
+						 hvpg_count);
 			payload = kzalloc(payload_sz, GFP_ATOMIC);
 			if (!payload)
 				return SCSI_MLQUEUE_DEVICE_BUSY;
Signature · 1 line
2.27.0
#1 lore raw

From: Gustavo A. R. Silva <[email protected]> Sent: Tuesday, January 25, 2022 11:42 AM

Quoted 19 lines

Make use of the struct_size() helper instead of an open-coded version, in order to avoid any potential type mistakes or integer overflows that, in the worst scenario, could lead to heap overflows.

Also, address the following sparse warnings:
drivers/scsi/storvsc_drv.c:1843:39: warning: using sizeof on a flexible structure

Link https://github.com/KSPP/linux/issues/174
Signed-off-by Gustavo A. R. Silva <[email protected]>
---
 drivers/scsi/storvsc_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
drivers/scsi/storvsc_drv.c +0 -0
index 9a0bba5a51a7..89c20dfc6609 100644

drivers/scsi/storvsc_drv.c static int storvsc_queuecommand(struct Scsi_Host *host, · line 1759

Quoted 6 lines
drivers/scsi/storvsc_drv.c +1 -1
@@ -1755,7 +1755,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host,
 struct scsi_cmnd *scmnd)
 	struct scatterlist *sgl;
 	struct vmscsi_request *vm_srb;
 	struct vmbus_packet_mpb_array  *payload;
-	u32 payload_sz;
+	size_t payload_sz;

Does changing this variable to type size_t accomplish anything? It will be stored into cmd_request->payload_sz, which is still a u32. The code in storvsc_do_io() and storvsc_command_completion() will process it as a 32 bit value.

Quoted 14 lines
drivers/scsi/storvsc_drv.c +0 -0
 	u32 length;
drivers/scsi/storvsc_drv.c +2 -2
 	if (vmstor_proto_version <= VMSTOR_PROTO_VERSION_WIN8) {

@@ -1839,8 +1839,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host,
 struct scsi_cmnd *scmnd)
 
 		if (hvpg_count > MAX_PAGE_BUFFER_COUNT) {
 
-			payload_sz = (hvpg_count * sizeof(u64) +
-				      sizeof(struct vmbus_packet_mpb_array));
+			payload_sz = struct_size(payload, range.pfn_array,
+						 hvpg_count);
 			payload = kzalloc(payload_sz, GFP_ATOMIC);
 			if (!payload)
Quoted 3 lines

return SCSI_MLQUEUE_DEVICE_BUSY;
--
2.27.0

Overall this is an incremental improvement. But the code is still implicitly dependent on scsi_bufflen() returning a 32-bit value into the local variable "length", and hence hvpg_count will always produce a payload_sz that fits in 32-bits.

I would be OK with taking this, minus the change to the type of the local variable payload_sz.

Michael