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- virtio_console: Fix poll/select blocking even though there is data to read

This commit is contained in:
Hans de Goede 2010-09-15 17:33:15 +02:00
parent db056c27c3
commit cb6f3ab735
2 changed files with 34 additions and 0 deletions
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5
kernel.spec
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@ -654,6 +654,7 @@ Patch800: linux-2.6-crash-driver.patch
# virt + ksm patches
Patch1555: fix_xen_guest_on_old_EC2.patch
Patch1556: linux-2.6.35.4-virtio_console-fix-poll.patch
# DRM
Patch1801: drm-revert-drm-fbdev-rework-output-polling-to-be-back-in-core.patch
@ -1293,6 +1294,7 @@ ApplyPatch linux-2.6-crash-driver.patch
# Assorted Virt Fixes
ApplyPatch fix_xen_guest_on_old_EC2.patch
ApplyPatch linux-2.6.35.4-virtio_console-fix-poll.patch
#ApplyPatch drm-revert-drm-fbdev-rework-output-polling-to-be-back-in-core.patch
#ApplyPatch revert-drm-kms-toggle-poll-around-switcheroo.patch
@ -1970,6 +1972,9 @@ fi
# and build.
%changelog
* Wed Sep 15 2010 Hans de Goede <hdegoede@redhat.com>
- virtio_console: Fix poll/select blocking even though there is data to read
* Tue Sep 14 2010 Chuck Ebbert <cebbert@redhat.com> 2.6.35.4-28
- Fix 3 CVEs:
/dev/sequencer open failure is not handled correctly (CVE-2010-3080)

29
linux-2.6.35.4-virtio_console-fix-poll.patch Normal file
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@ -0,0 +1,29 @@
Subject: virtio_console: Fix poll blocking even though there is data to read (version 2)
From: Hans de Goede <hdegoede@redhat.com>
I found this while working on a Linux agent for spice, the symptom I was
seeing was select blocking on the spice vdagent virtio serial port even
though there were messages queued up there.
virtio_console's port_fops_poll checks port->inbuf != NULL to determine if
read won't block. However if an application reads enough bytes from inbuf
through port_fops_read, to empty the current port->inbuf, port->inbuf
will be NULL even though there may be buffers left in the virtqueue.
This causes poll() to block even though there is data ready to be read, this
patch fixes this by using port_has_data(port) instead of the
port->inbuf != NULL check.
Signed-off-By: Hans de Goede <hdegoede@redhat.com>
diff -up linux-2.6.35.x86_64/drivers/char/virtio_console.c~ linux-2.6.35.x86_64/drivers/char/virtio_console.c
--- linux-2.6.35.x86_64/drivers/char/virtio_console.c~ 2010-08-02 00:11:14.000000000 +0200
+++ linux-2.6.35.x86_64/drivers/char/virtio_console.c 2010-09-15 13:39:29.043505000 +0200
@@ -642,7 +642,7 @@ static unsigned int port_fops_poll(struc
poll_wait(filp, &port->waitqueue, wait);
ret = 0;
- if (port->inbuf)
+ if (port_has_data(port))
ret |= POLLIN | POLLRDNORM;
if (!will_write_block(port))
ret |= POLLOUT;