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[PATCH 4.9 07/22] scsi: dont BUG_ON() empty DMA transfers

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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Thumshirn <jthumshirn@suse.de>

commit fd3fc0b4d7305fa7246622dcc0dec69c42443f45 upstream.

Don't crash the machine just because of an empty transfer. Use WARN_ON()
combined with returning an error.

Found by Dmitry Vyukov and syzkaller.

[ Changed to "WARN_ON_ONCE()". Al has a patch that should fix the root
  cause, but a BUG_ON() is not acceptable in any case, and a WARN_ON()
  might still be a cause of excessive log spamming.

  NOTE! If this warning ever triggers, we may end up leaking resources,
  since this doesn't bother to try to clean the command up. So this
  WARN_ON_ONCE() triggering does imply real problems. But BUG_ON() is
  much worse.

  People really need to stop using BUG_ON() for "this shouldn't ever
  happen". It makes pretty much any bug worse.     - Linus ]

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: James Bottomley <jejb@linux.vnet.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/scsi/scsi_lib.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1031,7 +1031,8 @@ int scsi_init_io(struct scsi_cmnd *cmd)
 	bool is_mq = (rq->mq_ctx != NULL);
 	int error;
 
-	BUG_ON(!rq->nr_phys_segments);
+	if (WARN_ON_ONCE(!rq->nr_phys_segments))
+		return -EINVAL;
 
 	error = scsi_init_sgtable(rq, &cmd->sdb);
 	if (error)

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[PATCH 4.9 00/22] 4.9.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 06/22] powerpc/64: Disable use of radix under a hypervisor Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 19/22] ntb: ntb_perf missing dmaengine_unmap_put Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 13/22] ARM: 8658/1: uaccess: fix zeroing of 64-bit get_user() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 16/22] printk: use rcuidle console tracepoint Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 17/22] timekeeping: Use deferred printk() in debug code Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 22/22] [media] videodev2.h: go back to limited range YCbCr for SRGB and, ADOBERGB Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 08/22] Fix missing sanity check in /dev/sg Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 21/22] bcache: Make gc wakeup sane, remove set_task_state() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 07/22] scsi: dont BUG_ON() empty DMA transfers Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 09/22] Input: elan_i2c - add ELAN0605 to the ACPI table Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 12/22] futex: Move futex_init() to core_initcall Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 02/22] [media] siano: make it work again with CONFIG_VMAP_STACK Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 14/22] Revert "i2c: designware: detect when dynamic tar update is possible" Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 01/22] vfs: fix uninitialized flags in splice_to_pipe() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 04/22] fuse: fix uninitialized flags in pipe_buffer Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 20/22] ntb_transport: Pick an unused queue Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 18/22] NTB: ntb_transport: fix debugfs_remove_recursive Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 05/22] mmc: core: fix multi-bit bus width without high-speed mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:10 +0100
  [PATCH 4.9 11/22] drm/dp/mst: fix kernel oops when turning off secondary monitor Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-21 14:20 +0100
  Re: [PATCH 4.9 00/22] 4.9.12-stable review Guenter Roeck <linux@roeck-us.net> - 2017-02-21 17:20 +0100
    Re: [PATCH 4.9 00/22] 4.9.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-23 18:00 +0100
  Re: [PATCH 4.9 00/22] 4.9.12-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-02-22 00:50 +0100
    Re: [PATCH 4.9 00/22] 4.9.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-23 18:00 +0100
  Re: [PATCH 4.9 00/22] 4.9.12-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-23 18:00 +0100

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