[Buildroot] [PATCH/2017.02.x 2/2] dbus: add upstream patch to fix startup hang with with expat >= 2.2.1
Sébastien Szymanski
sebastien.szymanski at armadeus.com
Mon Aug 14 08:40:57 UTC 2017
Yann, All,
>
> On 13 Aug 2017, at 14:56, Yann E. MORIN <yann.morin.1998 at free.fr> wrote:
>
> Sébastien, All,
>
> On 2017-08-10 15:47 +0200, Sébastien Szymanski spake thusly:
>> From: Marcus Hoffmann <m.hoffmann at cartelsol.com>
>> After c0ad6ded018ffbc33f7f5 expat: security bump to version 2.2.1
>> the system can hang on startup under certain circumstances.
>>
>> This happens when:
>> * we use systemd as init system
>> * the random nonblocking pool takes a while to initialize
>> * this apparently doesn't happen on qemu, so this would not have
>> been caught by the runtime testing infrastructure
>> * it also doesn't seem to happen when network booting
>>
>> For a more detailed description of the bug see here:
>> https://bugs.freedesktop.org/show_bug.cgi?id=101858
>>
>> The patch should be in next dbus version 1.10.24
>
> In the meantime. expat 2.2.3 has been released, which contrains (amongst
> other interesting stuff) commit 55839b633 (xmlparse.c: Read /dev/urandom
> if non-blocking getrandom failed), which ought to fix the boot delay.
>
> So, maybe it is beter to bumnpt expat instead, no? Or at least, backport
> that one commit.
expat is still at version 2.2.2 on the master branch.
I guess a patch needs to be first on the master branch before it can be backported on a LTS branch, isn’t it?
Regards,
Sébastien Szymanski
>
> Or did I miss something?
>
> Regards,
> Yann E. MORIN.
>
>> Set DBUS_AUTORECONF = YES because configure.ac is changed.
>>
>> Signed-off-by: Marcus Hoffmann <m.hoffmann at cartelsol.com>
>> [Arnout: add upstream commit sha + Marcus's Sob to the patch]
>> Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>
>>
>> (cherry picked from commit 5a5e76381f8b000baa09c902ca89d45725c47f04)
>> Signed-off-by: Sébastien Szymanski <sebastien.szymanski at armadeus.com>
>> ---
>> ...er-expat-Tell-Expat-not-to-defend-against.patch | 78 ++++++++++++++++++++++
>> package/dbus/dbus.mk | 3 +
>> 2 files changed, 81 insertions(+)
>> create mode 100644 package/dbus/0001-config-loader-expat-Tell-Expat-not-to-defend-against.patch
>>
>> diff --git a/package/dbus/0001-config-loader-expat-Tell-Expat-not-to-defend-against.patch b/package/dbus/0001-config-loader-expat-Tell-Expat-not-to-defend-against.patch
>> new file mode 100644
>> index 0000000..fd9e01d
>> --- /dev/null
>> +++ b/package/dbus/0001-config-loader-expat-Tell-Expat-not-to-defend-against.patch
>> @@ -0,0 +1,78 @@
>> +From 1252dc1d1f465b8ab6b36ff7252e395e66a040cf Mon Sep 17 00:00:00 2001
>> +From: Simon McVittie <smcv at debian.org>
>> +Date: Fri, 21 Jul 2017 10:46:39 +0100
>> +Subject: [PATCH 1/2] config-loader-expat: Tell Expat not to defend against
>> + hash collisions
>> +
>> +By default, Expat uses cryptographic-quality random numbers as a salt for
>> +its hash algorithm, and since 2.2.1 it gets them from the getrandom
>> +syscall on Linux. That syscall refuses to return any entropy until the
>> +kernel's CSPRNG (random pool) has been initialized. Unfortunately, this
>> +can take as long as 40 seconds on embedded devices with few entropy
>> +sources, which is too long: if the system dbus-daemon blocks for that
>> +length of time, important D-Bus clients like systemd and systemd-logind
>> +time out and fail to connect to it.
>> +
>> +We're parsing small configuration files here, and we trust them
>> +completely, so we don't need to defend against hash collisions: nobody
>> +is going to be crafting them to cause pathological performance.
>> +
>> +Bug: https://bugs.freedesktop.org/show_bug.cgi?id=101858
>> +Signed-off-by: Simon McVittie <smcv at debian.org>
>> +Tested-by: Christopher Hewitt <hewitt at ieee.org>
>> +Reviewed-by: Philip Withnall <withnall at endlessm.com>
>> +
>> +Upstream commit 1252dc1d1f465b8ab6b36ff7252e395e66a040cf
>> +Signed-off-by: Marcus Hoffmann <m.hoffmann at cartelsol.com>
>> +---
>> + bus/config-loader-expat.c | 14 ++++++++++++++
>> + configure.ac | 8 ++++++++
>> + 2 files changed, 22 insertions(+)
>> +
>> +diff --git a/bus/config-loader-expat.c b/bus/config-loader-expat.c
>> +index b571fda3..27cbe2d0 100644
>> +--- a/bus/config-loader-expat.c
>> ++++ b/bus/config-loader-expat.c
>> +@@ -203,6 +203,20 @@ bus_config_load (const DBusString *file,
>> + goto failed;
>> + }
>> +
>> ++ /* We do not need protection against hash collisions (CVE-2012-0876)
>> ++ * because we are only parsing trusted XML; and if we let Expat block
>> ++ * waiting for the CSPRNG to be initialized, as it does by default to
>> ++ * defeat CVE-2012-0876, it can cause timeouts during early boot on
>> ++ * entropy-starved embedded devices.
>> ++ *
>> ++ * TODO: When Expat gets a more explicit API for this than
>> ++ * XML_SetHashSalt, check for that too, and use it preferentially.
>> ++ * https://github.com/libexpat/libexpat/issues/91 */
>> ++#if defined(HAVE_XML_SETHASHSALT)
>> ++ /* Any nonzero number will do. https://xkcd.com/221/ */
>> ++ XML_SetHashSalt (expat, 4);
>> ++#endif
>> ++
>> + if (!_dbus_string_get_dirname (file, &dirname))
>> + {
>> + dbus_set_error (error, DBUS_ERROR_NO_MEMORY, NULL);
>> +diff --git a/configure.ac b/configure.ac
>> +index 52da11fb..c4022ed7 100644
>> +--- a/configure.ac
>> ++++ b/configure.ac
>> +@@ -938,6 +938,14 @@ XML_CFLAGS=
>> + AC_SUBST([XML_CFLAGS])
>> + AC_SUBST([XML_LIBS])
>> +
>> ++save_cflags="$CFLAGS"
>> ++save_libs="$LIBS"
>> ++CFLAGS="$CFLAGS $XML_CFLAGS"
>> ++LIBS="$LIBS $XML_LIBS"
>> ++AC_CHECK_FUNCS([XML_SetHashSalt])
>> ++CFLAGS="$save_cflags"
>> ++LIBS="$save_libs"
>> ++
>> + # Thread lib detection
>> + AC_ARG_VAR([THREAD_LIBS])
>> + save_libs="$LIBS"
>> +--
>> +2.11.0
>> +
>> diff --git a/package/dbus/dbus.mk b/package/dbus/dbus.mk
>> index e05fbff..f2974f2 100644
>> --- a/package/dbus/dbus.mk
>> +++ b/package/dbus/dbus.mk
>> @@ -6,6 +6,9 @@
>>
>> DBUS_VERSION = 1.10.22
>> DBUS_SITE = https://dbus.freedesktop.org/releases/dbus
>> +
>> +# 0001-config-loader-expat-Tell-Expat-not-to-defend-against.patch
>> +DBUS_AUTORECONF = YES
>> DBUS_LICENSE = AFLv2.1 or GPLv2+ (library, tools), GPLv2+ (tools)
>> DBUS_LICENSE_FILES = COPYING
>> DBUS_INSTALL_STAGING = YES
>> --
>> 2.7.3
>>
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>
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