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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Chris Leech <cleech@redhat.com>, Ming Lei <tom.leiming@gmail.com>,
	Dave Chinner <david@fromorbit.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Lee Duncan <lduncan@suse.com>,
	open-iscsi@googlegroups.com,
	Linux SCSI List <linux-scsi@vger.kernel.org>,
	linux-block <linux-block@vger.kernel.org>,
	Jens Axboe <axboe@fb.com>, "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0
Date: Fri, 23 Dec 2016 11:42:45 -0800	[thread overview]
Message-ID: <CA+55aFxA1LE+4jdR8YXZyRVJ-MpOCUVob=ESBsMPuW=Qb=px-A@mail.gmail.com> (raw)
In-Reply-To: <20161223100014.GA29467@lst.de>

On Fri, Dec 23, 2016 at 2:00 AM, Christoph Hellwig <hch@lst.de> wrote:
>
> From: Christoph Hellwig <hch@lst.de>
> Date: Fri, 23 Dec 2016 10:57:06 +0100
> Subject: virtio_blk: avoid DMA to stack for the sense buffer
>
> Most users of BLOCK_PC requests allocate the sense buffer on the stack,
> so to avoid DMA to the stack copy them to a field in the heap allocated
> virtblk_req structure.  Without that any attempt at SCSI passthrough I/O,
> including the SG_IO ioctl from userspace will crash the kernel.  Note that
> this includes running tools like hdparm even when the host does not have
> SCSI passthrough enabled.

Ugh. This patch is nasty.

I think we should just fix blk_execute_rq() instead.

But from a quick look, we also have at least sg_scsi_ioctl() and
sg_io() doing the same thing.

And the SG_IO thing in bsg_ioctl(). And spi_execute() in scsi_transport_spi.c

And resp_requests() in scsi_debug.c.

So I guess ugly it may need to be, and the rule is that the sense
buffer really can be on the stack and you can't DMA to/from it.
Comments from others?

                Linus

  reply	other threads:[~2016-12-23 19:49 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-12-14 22:24 [4.10, panic, regression] iscsi: null pointer deref at iscsi_tcp_segment_done+0x20d/0x2e0 Dave Chinner
2016-12-14 22:29 ` Dave Chinner
2016-12-16 18:59   ` Chris Leech
2016-12-21 22:16     ` Dave Chinner
2016-12-21 23:19       ` Linus Torvalds
2016-12-22  0:13         ` Chris Leech
2016-12-22  5:13           ` Dave Chinner
2016-12-22  5:46             ` Linus Torvalds
2016-12-22  6:50               ` Dave Chinner
2016-12-22 18:50                 ` Chris Leech
2016-12-22 23:53                   ` Ming Lei
2016-12-23  0:03                     ` Chris Leech
2016-12-23 10:00                       ` Christoph Hellwig
2016-12-23 19:42                         ` Linus Torvalds [this message]
2016-12-24  2:45                           ` Jens Axboe
2016-12-24  9:49                             ` Christoph Hellwig
2016-12-24 10:07                           ` Christoph Hellwig
2016-12-24 13:17                             ` Hannes Reinecke
2016-12-24 13:19                               ` Christoph Hellwig
2017-01-04 14:07                               ` Christoph Hellwig
2016-12-22 20:22               ` Hugh Dickins
2016-12-23  7:32                 ` Johannes Weiner
2016-12-23  8:33                   ` Johannes Weiner
2017-01-02 21:11                     ` Johannes Weiner
2017-01-03 12:28                       ` Jan Kara
2017-01-04 15:26                         ` Laurence Oberman
2017-01-04 17:38                           ` Laurence Oberman
2017-01-08  2:02                         ` Johannes Weiner
2017-01-08  2:17                           ` Linus Torvalds
2017-01-09 20:30                           ` Jan Kara
2017-01-09 20:45                             ` Johannes Weiner
2016-12-22  6:28             ` Dave Chinner
2016-12-22 17:24               ` Linus Torvalds
2016-12-22 20:20                 ` Thomas Gleixner
2016-12-22 20:42                 ` Dave Chinner
2016-12-22 21:06                   ` Dave Chinner
2016-12-22 21:10                     ` Linus Torvalds
2016-12-22 22:15                       ` Dave Chinner
2016-12-22 22:33                         ` Dave Chinner
2016-12-23  3:52                           ` Dave Chinner
2016-12-23  0:16                       ` Jens Axboe
2016-12-22  6:18         ` Christoph Hellwig
2016-12-22  6:30           ` Dave Chinner
2016-12-22  6:36             ` Christoph Hellwig

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