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[PATCH 4.5 033/238] sg: fix dxferp in from_to case

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

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

From: Douglas Gilbert <dgilbert@interlog.com>

commit 5ecee0a3ee8d74b6950cb41e8989b0c2174568d4 upstream.

One of the strange things that the original sg driver did was let the
user provide both a data-out buffer (it followed the sg_header+cdb)
_and_ specify a reply length greater than zero. What happened was that
the user data-out buffer was copied into some kernel buffers and then
the mid level was told a read type operation would take place with the
data from the device overwriting the same kernel buffers. The user would
then read those kernel buffers back into the user space.

>From what I can tell, the above action was broken by commit fad7f01e61bf
("sg: set dxferp to NULL for READ with the older SG interface") in 2008
and syzkaller found that out recently.

Make sure that a user space pointer is passed through when data follows
the sg_header structure and command.  Fix the abnormal case when a
non-zero reply_len is also given.

Fixes: fad7f01e61bf737fe8a3740d803f000db57ecac6
Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -652,7 +652,8 @@ sg_write(struct file *filp, const char _
 	else
 		hp->dxfer_direction = (mxsize > 0) ? SG_DXFER_FROM_DEV : SG_DXFER_NONE;
 	hp->dxfer_len = mxsize;
-	if (hp->dxfer_direction == SG_DXFER_TO_DEV)
+	if ((hp->dxfer_direction == SG_DXFER_TO_DEV) ||
+	    (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV))
 		hp->dxferp = (char __user *)buf + cmd_size;
 	else
 		hp->dxferp = NULL;

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[PATCH 4.5 000/238] 4.5.1-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 027/238] PCI: ACPI: IA64: fix IO port generic range check Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 001/238] x86/microcode/intel: Make early loader look for builtin microcode too Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 010/238] KVM: VMX: avoid guest hang on invalid invvpid instruction Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 033/238] sg: fix dxferp in from_to case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 023/238] s390/cpumf: add missing lpp magic initialization Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 024/238] s390/pci: enforce fmb page boundary rule Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 025/238] pinctrl-bcm2835: Fix cut-and-paste error in "pull" parsing Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 031/238] x86/iopl: Fix iopl capability check on Xen PV Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 026/238] PCI: Disable IO/MEM decoding for devices with non-compliant BARs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
    Re: [PATCH 4.5 026/238] PCI: Disable IO/MEM decoding for devices  with non-compliant BARs Ben Hutchings <ben@decadent.org.uk> - 2016-04-12 01:50 +0200
      Re: [PATCH 4.5 026/238] PCI: Disable IO/MEM decoding for devices  with non-compliant BARs Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-12 16:40 +0200
  [PATCH 4.5 022/238] s390: fix floating pointer register corruption (again) Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 019/238] sched/preempt, sh: kmap_coherent relies on disabled preemption Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 029/238] x86/apic: Fix suspicious RCU usage in smp_trace_call_function_interrupt() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  [PATCH 4.5 021/238] EDAC, amd64_edac: Shift wrapping issue in f1x_get_norm_dct_addr() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-10 23:00 +0200
  Re: [PATCH 4.5 000/238] 4.5.1-stable review Guenter Roeck <linux@roeck-us.net> - 2016-04-11 08:50 +0200
    Re: [PATCH 4.5 000/238] 4.5.1-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-12 16:40 +0200
  Re: [PATCH 4.5 000/238] 4.5.1-stable review shuahkh <shuahkh@osg.sisa.samsung.com> - 2016-04-11 19:30 +0200
    Re: [PATCH 4.5 000/238] 4.5.1-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-04-12 08:50 +0200

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