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64 lines
2.6 KiB
Diff
64 lines
2.6 KiB
Diff
From 7cc7ffd25d5e50b54cb942d07d4cb160f20ff9c5 Mon Sep 17 00:00:00 2001
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From: Martin Peres <martin.peres@linux.intel.com>
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Date: Fri, 17 Jul 2015 17:21:26 +0300
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Subject: [PATCH] os: make sure the clientsWritable fd_set is initialized
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before use
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In WaitForSomething(), the fd_set clientsWritable may be used unitialized when
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the boolean AnyClientsWriteBlocked is set in the WakeupHandler(). This leads to
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a crash in FlushAllOutput() after x11proto's commit
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2c94cdb453bc641246cc8b9a876da9799bee1ce7.
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The problem did not manifest before because both the XFD_SIZE and the maximum
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number of clients were set to 256. As the connectionTranslation table was
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initalized for the 256 clients to 0, the test on the index not being 0 was
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aborting before dereferencing the client #0.
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As of commit 2c94cdb453bc641246cc8b9a876da9799bee1ce7 in x11proto, the XFD_SIZE
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got bumped to 512. This lead the OutputPending fd_set to have any fd above 256
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to be uninitialized which in turns lead to reading an index after the end of
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the ConnectionTranslation table. This index would then be used to find the
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client corresponding to the fd marked as pending writes and would also result
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to an out-of-bound access which would usually be the fatal one.
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Fix this by zeroing the clientsWritable fd_set at the beginning of
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WaitForSomething(). In this case, the bottom part of the loop, which would
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indirectly call FlushAllOutput, will not do any work but the next call to
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select will result in the execution of the right codepath. This is exactly what
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we want because we need to know the writable clients before handling them. In
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the end, it also makes sure that the fds above MaxClient are initialized,
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preventing the crash in FlushAllOutput().
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Thanks to everyone involved in tracking this one down!
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Reported-by: Karol Herbst <freedesktop@karolherbst.de>
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Reported-by: Tobias Klausmann <tobias.klausmann@mni.thm.de>
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Signed-off-by: Martin Peres <martin.peres@linux.intel.com>
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Tested-by: Martin Peres <martin.peres@linux.intel.com>
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Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91316
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Cc: Ilia Mirkin <imirkin@alum.mit.edu>
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Cc: Martin Peres <martin.peres@linux.intel.com>
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Cc: Olivier Fourdan <ofourdan@redhat.com
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Cc: Adam Jackson <ajax@redhat.com>
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Cc: Alan Coopersmith <alan.coopersmith@oracle.com
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Cc: Chris Wilson <chris@chris-wilson.co.uk>
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---
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os/WaitFor.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/os/WaitFor.c b/os/WaitFor.c
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index 431f1a6..993c14e 100644
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--- a/os/WaitFor.c
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+++ b/os/WaitFor.c
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@@ -158,6 +158,7 @@ WaitForSomething(int *pClientsReady)
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Bool someReady = FALSE;
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FD_ZERO(&clientsReadable);
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+ FD_ZERO(&clientsWritable);
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if (nready)
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SmartScheduleStopTimer();
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--
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2.4.5
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