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

[Qiu-ji Chen <chenqiuji666@gmail.com>]

In line 1854 of the file esas2r_ioctl.c, the function 
esas2r_process_vda_ioctl() is called with the parameter vi being assigned 
the value of a->vda_buffer. On line 1892, a->vda_buffer is stored in DMA 
memory with the statement 
a->vda_buffer = dma_alloc_coherent(&a->pcid->dev, ..., indicating that the 
parameter vi passed to the function is also stored in DMA memory. This 
suggests that the parameter vi could be altered at any time by malicious 
hardware. If vi’s value is changed after the first conditional check 
if (vi->function >= vercnt), it is likely that an array out-of-bounds 
access could occur in the subsequent check 
if (vi->version > esas2r_vdaioctl_versions[vi_function]), leading to 
serious issues.

To fix this issue, we will store the value of vi->function in a local 
variable to ensure that the subsequent checks remain valid.

Signed-off-by: Qiu-ji Chen <chenqiuji666@gmail.com>
Cc: stable@vger.kernel.org
Fixes: 26780d9e12ed ("[SCSI] esas2r: ATTO Technology ExpressSAS 6G SAS/SATA RAID Adapter Driver")
---
 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