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[PATCH 4.10 43/48] drm/i915/gvt: Fix superfluous newline in GVT_DISPLAY_READY env var

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

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

From: Takashi Iwai <tiwai@suse.de>

commit d8e9b2b9097c117880dc22933239d05199c60b96 upstream.

send_display_send_uevent() sends two environment variable, and the
first one GVT_DISPLAY_READY is set including a new line at the end of
the string; that is obviously superfluous and wrong -- at least, it
*looks* so when you only read the code.

However, it doesn't appear in the actual output by a (supposedly
unexpected) trick.  The code uses snprintf() and truncates the string
in size 20 bytes.  This makes the string as GVT_DISPLAY_READY=0 or
...=1 including the trailing NUL-letter.  That is, the '\n' found in
the format string is always cut off as a result.

Although the code gives the correct result, it is confusing.  This
patch addresses it, just removing the superfluous '\n' from the format
string for avoiding further confusion.  If the argument "ready" were
not a  bool, the size 20 should be corrected as well.  But it's a
bool, so we can leave the magic number 20 as is for now.

FWIW, the bug was spotted by a new GCC7 warning:
  drivers/gpu/drm/i915/gvt/handlers.c: In function 'pvinfo_mmio_write':
  drivers/gpu/drm/i915/gvt/handlers.c:1042:34: error: 'snprintf' output truncated before the last format character [-Werror=format-truncation=]
    snprintf(display_ready_str, 20, "GVT_DISPLAY_READY=%d\n", ready);
                                    ^~~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/i915/gvt/handlers.c:1042:2: note: 'snprintf' output 21 bytes into a destination of size 20
    snprintf(display_ready_str, 20, "GVT_DISPLAY_READY=%d\n", ready);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 04d348ae3f0a ("drm/i915/gvt: vGPU display virtualization")
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1025903
Reported-by: Richard Biener <rguenther@suse.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/i915/gvt/handlers.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/gvt/handlers.c
+++ b/drivers/gpu/drm/i915/gvt/handlers.c
@@ -1039,7 +1039,7 @@ static int send_display_ready_uevent(str
 	char vmid_str[20];
 	char display_ready_str[20];
 
-	snprintf(display_ready_str, 20, "GVT_DISPLAY_READY=%d\n", ready);
+	snprintf(display_ready_str, 20, "GVT_DISPLAY_READY=%d", ready);
 	env[0] = display_ready_str;
 
 	snprintf(vmid_str, 20, "VMID=%d", vgpu->id);

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[PATCH 4.10 00/48] 4.10.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:40 +0100
  [PATCH 4.10 23/48] powerpc/booke: Fix boot crash due to null hugepd Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:40 +0100
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  [PATCH 4.10 30/48] usb: gadget: function: f_fs: pass companion descriptor along Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:40 +0100
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  [PATCH 4.10 44/48] [media] serial_ir: ensure were ready to receive interrupts Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
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  [PATCH 4.10 35/48] USB: serial: omninet: fix reference leaks at open Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
  [PATCH 4.10 38/48] USB: serial: io_ti: fix NULL-deref in interrupt callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
  [PATCH 4.10 08/48] MIPS: ip27: Disable qlge driver in defconfig Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
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  [PATCH 4.10 45/48] dm: flush queued bios when process blocks to avoid deadlock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
  [PATCH 4.10 43/48] drm/i915/gvt: Fix superfluous newline in GVT_DISPLAY_READY env var Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
  [PATCH 4.10 06/48] MIPS: Update defconfigs for NF_CT_PROTO_DCCP/UDPLITE change Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
  [PATCH 4.10 25/48] PCI: Prevent VPD access for QLogic ISP2722 Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
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  [PATCH 4.10 32/48] usb: host: xhci-dbg: HCIVERSION should be a binary number Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 15:50 +0100
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  [PATCH 4.10 13/48] MIPS: ralink: Cosmetic change to prom_init(). Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 16:00 +0100
  [PATCH 4.10 02/48] ARM: qcom_defconfig: Enable RPM/RPM-SMD clocks Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-16 16:00 +0100
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  Re: [PATCH 4.10 00/48] 4.10.4-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-03-16 20:40 +0100
    Re: [PATCH 4.10 00/48] 4.10.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-17 02:50 +0100
  Re: [PATCH 4.10 00/48] 4.10.4-stable review Guenter Roeck <linux@roeck-us.net> - 2017-03-16 23:40 +0100
    Re: [PATCH 4.10 00/48] 4.10.4-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-17 02:50 +0100

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