[PATCH v2] [SCSI] esas2r: fix possible array out-of-bounds caused by bad DMA value in esas2r_process_vda_ioctl()

[PATCH v2] [SCSI] esas2r: fix possible array out-of-bounds caused by bad DMA value in esas2r_process_vda_ioctl()

[Qiu-ji Chen]

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")
---
V2:
Changed the incorrect patch title
---
 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

Re: [PATCH v2] [SCSI] esas2r: fix possible array out-of-bounds caused by bad DMA value in esas2r_process_vda_ioctl()

[James Bottomley]

On Thu, 2024-11-07 at 22:16 +0800, Qiu-ji Chen wrote:
> 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.

Absent a specific threat (such as TPM with an interposer) this isn't a
vector the kernel protects against (we have to believe what hardware
says unless we know it to be specifically buggy about something). 
However, even supposing a PCI Interposer were considered a threat, the
answer now is hardware based: SPDM/PCI-IDE.

Regards,

James