CVE-2022-49073

In the Linux kernel, the following vulnerability has been resolved:

ata: sata_dwc_460ex: Fix crash due to OOB write

the driver uses libata's "tag" values from in various arrays.

Since the mentioned patch bumped the ATA_TAG_INTERNAL to 32,

the value of the SATA_DWC_QCMD_MAX needs to account for that.

Otherwise ATA_TAG_INTERNAL usage cause similar crashes like

this as reported by Tice Rex on the OpenWrt Forum and

reproduced (with symbols) here:

| BUG: Kernel NULL pointer dereference at 0x00000000

| Faulting instruction address: 0xc03ed4b8

| Oops: Kernel access of bad area, sig: 11 [#1]

| BE PAGE_SIZE=4K PowerPC 44x Platform

| CPU: 0 PID: 362 Comm: scsi_eh_1 Not tainted 5.4.163 #0

| NIP: c03ed4b8 LR: c03d27e8 CTR: c03ed36c

| REGS: cfa59950 TRAP: 0300 Not tainted (5.4.163)

| MSR: 00021000 <CE,ME> CR: 42000222 XER: 00000000

| DEAR: 00000000 ESR: 00000000

| GPR00: c03d27e8 cfa59a08 cfa55fe0 00000000 0fa46bc0 [...]

| [..]

| NIP [c03ed4b8] sata_dwc_qc_issue+0x14c/0x254

| LR [c03d27e8] ata_qc_issue+0x1c8/0x2dc

| Call Trace:

| [cfa59a08] [c003f4e0] __cancel_work_timer+0x124/0x194 (unreliable)

| [cfa59a78] [c03d27e8] ata_qc_issue+0x1c8/0x2dc

| [cfa59a98] [c03d2b3c] ata_exec_internal_sg+0x240/0x524

| [cfa59b08] [c03d2e98] ata_exec_internal+0x78/0xe0

| [cfa59b58] [c03d30fc] ata_read_log_page.part.38+0x1dc/0x204

| [cfa59bc8] [c03d324c] ata_identify_page_supported+0x68/0x130

| [...]

This is because sata_dwc_dma_xfer_complete() NULLs the

dma_pending's next neighbour "chan" (a *dma_chan struct) in

this '32' case right here (line ~735):

> hsdevp->dma_pending[tag] = SATA_DWC_DMA_PENDING_NONE;

Then the next time, a dma gets issued; dma_dwc_xfer_setup() passes

the NULL'd hsdevp->chan to the dmaengine_slave_config() which then

causes the crash.

With this patch, SATA_DWC_QCMD_MAX is now set to ATA_MAX_QUEUE + 1.

This avoids the OOB. But please note, there was a worthwhile discussion

on what ATA_TAG_INTERNAL and ATA_MAX_QUEUE is. And why there should not

be a "fake" 33 command-long queue size.

Ideally, the dw driver should account for the ATA_TAG_INTERNAL.

In Damien Le Moal's words: "... having looked at the driver, it

is a bigger change than just faking a 33rd "tag" that is in fact

not a command tag at all."

BugLink: https://github.com/openwrt/openwrt/issues/9505