mainlining shenanigans
7aa8104a55
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."
Fixes:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.