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From f06f903d5cb3c14853a7213b6a70c078380b7a62 Mon Sep 17 00:00:00 2001
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Message-Id: <f06f903d5cb3c14853a7213b6a70c078380b7a62@dist-git>
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From: Michal Privoznik <mprivozn@redhat.com>
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Date: Fri, 24 Jan 2020 15:05:50 +0100
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Subject: [PATCH] qemu_conf: Avoid dereferencing NULL in
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 virQEMUDriverGetHost{NUMACaps, CPU}
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When fixing [1] I've ran attached reproducer and had it spawn
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1024 threads and query capabilities XML in each one of them. This
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lead libvirtd to hit the RLIMIT_NOFILE limit which was kind of
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expected. What wasn't expected was a subsequent segfault. It
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happened because virCPUProbeHost failed and returned NULL. We've
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taken the NULL and passed it to virCapabilitiesHostNUMARef()
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which dereferenced it. Code inspection showed the same flas in
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virQEMUDriverGetHostNUMACaps(), so I'm fixing both places.
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1: https://bugzilla.redhat.com/show_bug.cgi?id=1791790
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Reviewed-by: Peter Krempa <pkrempa@redhat.com>
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(cherry picked from commit cc361a34c53210d682dbc5f2d506b4a23b71e399)
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https://bugzilla.redhat.com/show_bug.cgi?id=1794691
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Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
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Message-Id: <5de22b27463cd2803b3910d7ef45a0e4bc08ad47.1579874719.git.mprivozn@redhat.com>
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Reviewed-by: Jiri Denemark <jdenemar@redhat.com>
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---
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 src/qemu/qemu_conf.c | 18 ++++++++++++++----
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 1 file changed, 14 insertions(+), 4 deletions(-)
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diff --git a/src/qemu/qemu_conf.c b/src/qemu/qemu_conf.c
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index 3d2f0e7bbb..e33ef4895e 100644
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--- a/src/qemu/qemu_conf.c
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+++ b/src/qemu/qemu_conf.c
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@@ -1201,32 +1201,42 @@ virQEMUDriverCreateXMLConf(virQEMUDriverPtr driver,
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 virCapsHostNUMAPtr
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 virQEMUDriverGetHostNUMACaps(virQEMUDriverPtr driver)
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 {
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+    virCapsHostNUMAPtr hostnuma;
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+
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     qemuDriverLock(driver);
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     if (!driver->hostnuma)
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         driver->hostnuma = virCapabilitiesHostNUMANewHost();
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+    hostnuma = driver->hostnuma;
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+
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     qemuDriverUnlock(driver);
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-    virCapabilitiesHostNUMARef(driver->hostnuma);
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+    if (hostnuma)
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+        virCapabilitiesHostNUMARef(hostnuma);
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-    return driver->hostnuma;
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+    return hostnuma;
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 }
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 virCPUDefPtr
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 virQEMUDriverGetHostCPU(virQEMUDriverPtr driver)
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 {
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+    virCPUDefPtr hostcpu;
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+
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     qemuDriverLock(driver);
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     if (!driver->hostcpu)
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         driver->hostcpu = virCPUProbeHost(virArchFromHost());
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+    hostcpu = driver->hostcpu;
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+
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     qemuDriverUnlock(driver);
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-    virCPUDefRef(driver->hostcpu);
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+    if (hostcpu)
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+        virCPUDefRef(hostcpu);
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-    return driver->hostcpu;
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+    return hostcpu;
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 }
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-- 
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2.25.0
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