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commit14e3062fb1upstream. Avoid that scsi_show_rq() triggers a NULL pointer dereference if called after sd_uninit_command(). Swap the NULL pointer assignment and the mempool_free() call in sd_uninit_command() to make it less likely that scsi_show_rq() triggers a use-after-free. Note: even with these changes scsi_show_rq() can trigger a use-after-free but that's a lesser evil than e.g. suppressing debug information for T10 PI Type 2 commands completely. This patch fixes the following oops: BUG: unable to handle kernel NULL pointer dereference at (null) IP: scsi_format_opcode_name+0x1a/0x1c0 CPU: 1 PID: 1881 Comm: cat Not tainted 4.14.0-rc2.blk_mq_io_hang+ #516 Call Trace: __scsi_format_command+0x27/0xc0 scsi_show_rq+0x5c/0xc0 __blk_mq_debugfs_rq_show+0x116/0x130 blk_mq_debugfs_rq_show+0xe/0x10 seq_read+0xfe/0x3b0 full_proxy_read+0x54/0x90 __vfs_read+0x37/0x160 vfs_read+0x96/0x130 SyS_read+0x55/0xc0 entry_SYSCALL_64_fastpath+0x1a/0xa5 [mkp: added Type 2] Fixes:0eebd005dd("scsi: Implement blk_mq_ops.show_rq()") Reported-by: Ming Lei <ming.lei@redhat.com> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Cc: James E.J. Bottomley <jejb@linux.vnet.ibm.com> Cc: Martin K. Petersen <martin.petersen@oracle.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.com> Cc: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.