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From: tip-bot for Brandon Phiilps on 10 Feb 2010 17:50
Commit-ID: ced5b697a76d325e7a7ac7d382dbbb632c765093
Gitweb: http://git.kernel.org/tip/ced5b697a76d325e7a7ac7d382dbbb632c765093
Author: Brandon Phiilps <bphilips(a)suse.de>
AuthorDate: Wed, 10 Feb 2010 01:20:06 -0800
Committer: H. Peter Anvin <hpa(a)zytor.com>
CommitDate: Wed, 10 Feb 2010 14:27:28 -0800

x86: Avoid race condition in pci_enable_msix()

Keep chip_data in create_irq_nr and destroy_irq.

When two drivers are setting up MSI-X at the same time via
pci_enable_msix() there is a race. See this dmesg excerpt:

[ 85.170610] ixgbe 0000:02:00.1: irq 97 for MSI/MSI-X
[ 85.170611] alloc irq_desc for 99 on node -1
[ 85.170613] igb 0000:08:00.1: irq 98 for MSI/MSI-X
[ 85.170614] alloc kstat_irqs on node -1
[ 85.170616] alloc irq_2_iommu on node -1
[ 85.170617] alloc irq_desc for 100 on node -1
[ 85.170619] alloc kstat_irqs on node -1
[ 85.170621] alloc irq_2_iommu on node -1
[ 85.170625] ixgbe 0000:02:00.1: irq 99 for MSI/MSI-X
[ 85.170626] alloc irq_desc for 101 on node -1
[ 85.170628] igb 0000:08:00.1: irq 100 for MSI/MSI-X
[ 85.170630] alloc kstat_irqs on node -1
[ 85.170631] alloc irq_2_iommu on node -1
[ 85.170635] alloc irq_desc for 102 on node -1
[ 85.170636] alloc kstat_irqs on node -1
[ 85.170639] alloc irq_2_iommu on node -1
[ 85.170646] BUG: unable to handle kernel NULL pointer dereference
at 0000000000000088

As you can see igb and ixgbe are both alternating on create_irq_nr()
via pci_enable_msix() in their probe function.

ixgbe: While looping through irq_desc_ptrs[] via create_irq_nr() ixgbe
choses irq_desc_ptrs[102] and exits the loop, drops vector_lock and
calls dynamic_irq_init. Then it sets irq_desc_ptrs[102]->chip_data =
NULL via dynamic_irq_init().

igb: Grabs the vector_lock now and starts looping over irq_desc_ptrs[]
via create_irq_nr(). It gets to irq_desc_ptrs[102] and does this:

cfg_new = irq_desc_ptrs[102]->chip_data;
if (cfg_new->vector != 0)
continue;

This hits the NULL deref.

Another possible race exists via pci_disable_msix() in a driver or in
the number of error paths that call free_msi_irqs():

destroy_irq()
dynamic_irq_cleanup() which sets desc->chip_data = NULL
....race window...
desc->chip_data = cfg;

Remove the save and restore code for cfg in create_irq_nr() and
destroy_irq() and take the desc->lock when checking the irq_cfg.

Reported-and-analyzed-by: Brandon Philips <bphilips(a)suse.de>
Signed-off-by: Yinghai Lu <yinghai(a)kernel.org>
LKML-Reference: <1265793639-15071-3-git-send-email-yinghai(a)kernel.org>
Signed-off-by: Brandon Phililps <bphilips(a)suse.de>
Cc: stable(a)kernel.org
Signed-off-by: H. Peter Anvin <hpa(a)zytor.com>
---
arch/x86/kernel/apic/io_apic.c | 18 ++++----------
include/linux/irq.h | 2 +
kernel/irq/chip.c | 52 +++++++++++++++++++++++++++++++++-------
3 files changed, 50 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 53243ca..c86591b 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -3228,12 +3228,9 @@ unsigned int create_irq_nr(unsigned int irq_want, int node)
}
spin_unlock_irqrestore(&vector_lock, flags);

- if (irq > 0) {
- dynamic_irq_init(irq);
- /* restore it, in case dynamic_irq_init clear it */
- if (desc_new)
- desc_new->chip_data = cfg_new;
- }
+ if (irq > 0)
+ dynamic_irq_init_keep_chip_data(irq);
+
return irq;
}

@@ -3256,17 +3253,12 @@ void destroy_irq(unsigned int irq)
{
unsigned long flags;
struct irq_cfg *cfg;
- struct irq_desc *desc;

- /* store it, in case dynamic_irq_cleanup clear it */
- desc = irq_to_desc(irq);
- cfg = desc->chip_data;
- dynamic_irq_cleanup(irq);
- /* connect back irq_cfg */
- desc->chip_data = cfg;
+ dynamic_irq_cleanup_keep_chip_data(irq);

free_irte(irq);
spin_lock_irqsave(&vector_lock, flags);
+ cfg = irq_to_desc(irq)->chip_data;
__clear_irq_vector(irq, cfg);
spin_unlock_irqrestore(&vector_lock, flags);
}
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 451481c..4d9b26e 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -400,7 +400,9 @@ static inline int irq_has_action(unsigned int irq)

/* Dynamic irq helper functions */
extern void dynamic_irq_init(unsigned int irq);
+void dynamic_irq_init_keep_chip_data(unsigned int irq);
extern void dynamic_irq_cleanup(unsigned int irq);
+void dynamic_irq_cleanup_keep_chip_data(unsigned int irq);

/* Set/get chip/data for an IRQ: */
extern int set_irq_chip(unsigned int irq, struct irq_chip *chip);
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index ecc3fa2..d70394f 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -18,11 +18,7 @@

#include "internals.h"

-/**
- * dynamic_irq_init - initialize a dynamically allocated irq
- * @irq: irq number to initialize
- */
-void dynamic_irq_init(unsigned int irq)
+static void dynamic_irq_init_x(unsigned int irq, bool keep_chip_data)
{
struct irq_desc *desc;
unsigned long flags;
@@ -41,7 +37,8 @@ void dynamic_irq_init(unsigned int irq)
desc->depth = 1;
desc->msi_desc = NULL;
desc->handler_data = NULL;
- desc->chip_data = NULL;
+ if (!keep_chip_data)
+ desc->chip_data = NULL;
desc->action = NULL;
desc->irq_count = 0;
desc->irqs_unhandled = 0;
@@ -55,10 +52,26 @@ void dynamic_irq_init(unsigned int irq)
}

/**
- * dynamic_irq_cleanup - cleanup a dynamically allocated irq
+ * dynamic_irq_init - initialize a dynamically allocated irq
* @irq: irq number to initialize
*/
-void dynamic_irq_cleanup(unsigned int irq)
+void dynamic_irq_init(unsigned int irq)
+{
+ dynamic_irq_init_x(irq, false);
+}
+
+/**
+ * dynamic_irq_init_keep_chip_data - initialize a dynamically allocated irq
+ * @irq: irq number to initialize
+ *
+ * does not set irq_to_desc(irq)->chip_data to NULL
+ */
+void dynamic_irq_init_keep_chip_data(unsigned int irq)
+{
+ dynamic_irq_init_x(irq, true);
+}
+
+static void dynamic_irq_cleanup_x(unsigned int irq, bool keep_chip_data)
{
struct irq_desc *desc = irq_to_desc(irq);
unsigned long flags;
@@ -77,7 +90,8 @@ void dynamic_irq_cleanup(unsigned int irq)
}
desc->msi_desc = NULL;
desc->handler_data = NULL;
- desc->chip_data = NULL;
+ if (!keep_chip_data)
+ desc->chip_data = NULL;
desc->handle_irq = handle_bad_irq;
desc->chip = &no_irq_chip;
desc->name = NULL;
@@ -85,6 +99,26 @@ void dynamic_irq_cleanup(unsigned int irq)
raw_spin_unlock_irqrestore(&desc->lock, flags);
}

+/**
+ * dynamic_irq_cleanup - cleanup a dynamically allocated irq
+ * @irq: irq number to initialize
+ */
+void dynamic_irq_cleanup(unsigned int irq)
+{
+ dynamic_irq_cleanup_x(irq, false);
+}
+
+/**
+ * dynamic_irq_cleanup_keep_chip_data - cleanup a dynamically allocated irq
+ * @irq: irq number to initialize
+ *
+ * does not set irq_to_desc(irq)->chip_data to NULL
+ */
+void dynamic_irq_cleanup_keep_chip_data(unsigned int irq)
+{
+ dynamic_irq_cleanup_x(irq, true);
+}
+

/**
* set_irq_chip - set the irq chip for an irq
--
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Prev: oom: select task from tasklist for mempolicy ooms
Next: linux-next: manual merge of the i.MX tree with Linus' tree