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This fixes a potential race condition observed on Power systems. Several places throughout the aacraid driver call aac_fib_send or similar to send a command to the aacraid adapter, then check the return code to determine if the command was actually sent to the adapter, then update the phase field in the scsi command scratch pad area to track that the firmware now owns this command. However, there is nothing that ensures that by the time the aac_fib_send function returns and we go to write to the scsi command, that the command hasn't already completed and the scsi command has been freed. This was causing random crashes in the TCP stack which was tracked down to be caused by memory that had been a struct request + scsi_cmnd being now used for an skbuff. Memory poisoning was enabled in the kernel to debug this which showed that the last owner of the memory that had been freed was aacraid and that it was a struct request. The memory that was corrupted was the exact data pattern of AAC_OWNER_FIRMWARE and it was at the same offset that aacraid writes, which is scsicmd->SCp.phase. The patch below resolves this issue. Cc: <stable@vger.kernel.org> Signed-off-by: Brian King <brking@linux.vnet.ibm.com> Tested-by: Wen Xiong <wenxiong@linux.vnet.ibm.com> Reviewed-by: Dave Carroll <david.carroll@microsemi.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.