From: Tomoki Sekiyama Date: Thu, 26 Jul 2012 10:47:32 +0000 (+0900) Subject: x86/ioapic: Fix NULL pointer dereference on CPU hotplug after disabling irqs X-Git-Tag: v3.6-rc2~36^2~4 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1d44b30f35a9873a65b320dd5300088fa995fd94;p=pandora-kernel.git x86/ioapic: Fix NULL pointer dereference on CPU hotplug after disabling irqs In the current kernel, percpu variable `vector_irq' is not always cleared when a CPU is offlined. If the CPU that has the disabled irqs in vector_irq is hotplugged again, __setup_vector_irq() hits invalid irq vector and may crash. This bug can be reproduced as following; # echo 0 > /sys/devices/system/cpu/cpu7/online # modprobe -r some_driver_using_interrupts # vector_irq@cpu7 uncleared # echo 1 > /sys/devices/system/cpu/cpu7/online # kernel may crash To fix this problem, this patch clears vector_irq in __fixup_irqs() when the CPU is offlined. This also reverts commit f6175f5bfb4c, which partially fixes this bug by clearing vector in __clear_irq_vector(). But in environments with IOMMU IRQ remapper, it could fail because cfg->domain doesn't contain offlined CPUs. With this patch, the fix in __clear_irq_vector() can be reverted because every vector_irq is already cleared in __fixup_irqs() on offlined CPUs. Signed-off-by: Tomoki Sekiyama Acked-by: Suresh Siddha Cc: yrl.pp-manager.tt@hitachi.com Cc: Yinghai Lu Cc: Alexander Gordeev Link: http://lkml.kernel.org/r/20120726104732.2889.19144.stgit@kvmdev Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed