[PATCH] [SCSI] esas2r: fix possible buffer overflow caused by bad DMA value in esas2r_process_vda_ioctl()

[Huai-Yuan Liu]

The value vi->function is stored in DMA memory, so it can be modified at
any time by malicious hardware. In this case, "if (vi->function >= vercnt)"
can be passed, which may cause buffer overflow and other unexpected 
execution results in the following code.

To address this issue, vi->function should be assigned to a local value,
which replaces the use of vi->function.

Fixes: 26780d9e12ed ("[SCSI] esas2r: ATTO Technology ExpressSAS 6G SAS/SATA RAID Adapter Driver")
Signed-off-by: Huai-Yuan Liu <qq810974084@xxxxxxxxx>
---
 drivers/scsi/esas2r/esas2r_vda.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/scsi/esas2r/esas2r_vda.c b/drivers/scsi/esas2r/esas2r_vda.c
index 30028e56df63..48af8c05b01d 100644
--- a/drivers/scsi/esas2r/esas2r_vda.c
+++ b/drivers/scsi/esas2r/esas2r_vda.c
@@ -70,16 +70,17 @@ bool esas2r_process_vda_ioctl(struct esas2r_adapter *a,
 	u32 datalen = 0;
 	struct atto_vda_sge *firstsg = NULL;
 	u8 vercnt = (u8)ARRAY_SIZE(esas2r_vdaioctl_versions);
+	u8 vi_function = vi->function;
 
 	vi->status = ATTO_STS_SUCCESS;
 	vi->vda_status = RS_PENDING;
 
-	if (vi->function >= vercnt) {
+	if (vi_function >= vercnt) {
 		vi->status = ATTO_STS_INV_FUNC;
 		return false;
 	}
 
-	if (vi->version > esas2r_vdaioctl_versions[vi->function]) {
+	if (vi->version > esas2r_vdaioctl_versions[vi_function]) {
 		vi->status = ATTO_STS_INV_VERSION;
 		return false;
 	}
@@ -89,14 +90,14 @@ bool esas2r_process_vda_ioctl(struct esas2r_adapter *a,
 		return false;
 	}
 
-	if (vi->function != VDA_FUNC_SCSI)
+	if (vi_function != VDA_FUNC_SCSI)
 		clear_vda_request(rq);
 
-	rq->vrq->scsi.function = vi->function;
+	rq->vrq->scsi.function = vi_function;
 	rq->interrupt_cb = esas2r_complete_vda_ioctl;
 	rq->interrupt_cx = vi;
 
-	switch (vi->function) {
+	switch (vi_function) {
 	case VDA_FUNC_FLASH:
 
 		if (vi->cmd.flash.sub_func != VDA_FLASH_FREAD
-- 
2.34.1