From ba068938e629eb1a8b423a54405233e685cedb78 Mon Sep 17 00:00:00 2001
Message-Id: <ba068938e629eb1a8b423a54405233e685cedb78.1647594132.git.chunkeey@gmail.com>
From: Christian Lamparter <chunkeey@gmail.com>
Date: Thu, 17 Mar 2022 21:29:28 +0100
Subject: [PATCH v1 1/2] ata: sata_dwc_460ex: Fix crash due to OOB write
To: linux-ide@vger.kernel.org
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>,
    Jens Axboe <axboe@kernel.dk>,
    Tejun Heo <tj@kernel.org>,
    Andy Shevchenko <andriy.shevchenko@linux.intel.com>

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 be bumped to 33.

Otherwise ATA_TAG_INTERNAL cause a crash like this:

| 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.

Reported-by: ticerex (OpenWrt Forum)
Fixes: 28361c403683c ("libata: add extra internal command")
Cc: stable@kernel.org # 4.18+
Link: https://forum.openwrt.org/t/my-book-live-duo-reboot-loop/122464
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
---
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -145,7 +145,7 @@ struct sata_dwc_device {
 #endif
 };
 
-#define SATA_DWC_QCMD_MAX	32
+#define SATA_DWC_QCMD_MAX	33
 
 struct sata_dwc_device_port {
 	struct sata_dwc_device	*hsdev;