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Phil Oester reported that a fix for a possible buffer overrun that I sent caused a regression that manifests in this output: Event Message: A PCI parity error was detected on a component at bus 0 device 5 function 0. Severity: Critical Message ID: PCI1308 The original code tried to handle the sense data pointer differently when using 32-bit 64-bit DMA addressing, which would lead to a 32-bit dma_addr_t value of 0x11223344 to get stored 32-bit kernel: 44 33 22 11 ?? ?? ?? ?? 64-bit LE kernel: 44 33 22 11 00 00 00 00 64-bit BE kernel: 00 00 00 00 44 33 22 11 or a 64-bit dma_addr_t value of 0x1122334455667788 to get stored as 32-bit kernel: 88 77 66 55 ?? ?? ?? ?? 64-bit kernel: 88 77 66 55 44 33 22 11 In my patch, I tried to ensure that the same value is used on both 32-bit and 64-bit kernels, and picked what seemed to be the most sensible combination, storing 32-bit addresses in the first four bytes (as 32-bit kernels already did), and 64-bit addresses in eight consecutive bytes (as 64-bit kernels already did), but evidently this was incorrect. Always storing the dma_addr_t pointer as 64-bit little-endian, i.e. initializing the second four bytes to zero in case of 32-bit addressing, apparently solved the problem for Phil, and is consistent with what all 64-bit little-endian machines did before. I also checked in the history that in previous versions of the code, the pointer was always in the first four bytes without padding, and that previous attempts to fix 64-bit user space, big-endian architectures and 64-bit DMA were clearly flawed and seem to have introduced made this worse. Link: https://lore.kernel.org/r/20210104234137.438275-1-arnd@kernel.org Fixes:381d34e376("scsi: megaraid_sas: Check user-provided offsets") Fixes:107a60dd71("scsi: megaraid_sas: Add support for 64bit consistent DMA") Fixes:94cd65ddf4("[SCSI] megaraid_sas: addded support for big endian architecture") Fixes:7b2519afa1("[SCSI] megaraid_sas: fix 64 bit sense pointer truncation") Reported-by: Phil Oester <kernel@linuxace.com> Tested-by: Phil Oester <kernel@linuxace.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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.