Patch "x86/ioapic: Handle allocation failures gracefully" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    x86/ioapic: Handle allocation failures gracefully

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-ioapic-handle-allocation-failures-gracefully.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cdfc3389b7095a14cec63b07faadcf98ce5caa4f
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date:   Fri Aug 2 18:15:34 2024 +0200

    x86/ioapic: Handle allocation failures gracefully
    
    [ Upstream commit 830802a0fea8fb39d3dc9fb7d6b5581e1343eb1f ]
    
    Breno observed panics when using failslab under certain conditions during
    runtime:
    
       can not alloc irq_pin_list (-1,0,20)
       Kernel panic - not syncing: IO-APIC: failed to add irq-pin. Can not proceed
    
       panic+0x4e9/0x590
       mp_irqdomain_alloc+0x9ab/0xa80
       irq_domain_alloc_irqs_locked+0x25d/0x8d0
       __irq_domain_alloc_irqs+0x80/0x110
       mp_map_pin_to_irq+0x645/0x890
       acpi_register_gsi_ioapic+0xe6/0x150
       hpet_open+0x313/0x480
    
    That's a pointless panic which is a leftover of the historic IO/APIC code
    which panic'ed during early boot when the interrupt allocation failed.
    
    The only place which might justify panic is the PIT/HPET timer_check() code
    which tries to figure out whether the timer interrupt is delivered through
    the IO/APIC. But that code does not require to handle interrupt allocation
    failures. If the interrupt cannot be allocated then timer delivery fails
    and it either panics due to that or falls back to legacy mode.
    
    Cure this by removing the panic wrapper around __add_pin_to_irq_node() and
    making mp_irqdomain_alloc() aware of the failure condition and handle it as
    any other failure in this function gracefully.
    
    Reported-by: Breno Leitao <leitao@xxxxxxxxxx>
    Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
    Tested-by: Breno Leitao <leitao@xxxxxxxxxx>
    Tested-by: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
    Link: https://lore.kernel.org/all/ZqfJmUF8sXIyuSHN@xxxxxxxxx
    Link: https://lore.kernel.org/all/20240802155440.275200843@xxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index bb71b628edcb4..586ea838a5a15 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -350,27 +350,26 @@ static void ioapic_mask_entry(int apic, int pin)
  * shared ISA-space IRQs, so we have to support them. We are super
  * fast in the common case, and fast for shared ISA-space IRQs.
  */
-static int __add_pin_to_irq_node(struct mp_chip_data *data,
-				 int node, int apic, int pin)
+static bool add_pin_to_irq_node(struct mp_chip_data *data, int node, int apic, int pin)
 {
 	struct irq_pin_list *entry;
 
-	/* don't allow duplicates */
-	for_each_irq_pin(entry, data->irq_2_pin)
+	/* Don't allow duplicates */
+	for_each_irq_pin(entry, data->irq_2_pin) {
 		if (entry->apic == apic && entry->pin == pin)
-			return 0;
+			return true;
+	}
 
 	entry = kzalloc_node(sizeof(struct irq_pin_list), GFP_ATOMIC, node);
 	if (!entry) {
-		pr_err("can not alloc irq_pin_list (%d,%d,%d)\n",
-		       node, apic, pin);
-		return -ENOMEM;
+		pr_err("Cannot allocate irq_pin_list (%d,%d,%d)\n", node, apic, pin);
+		return false;
 	}
+
 	entry->apic = apic;
 	entry->pin = pin;
 	list_add_tail(&entry->list, &data->irq_2_pin);
-
-	return 0;
+	return true;
 }
 
 static void __remove_pin_from_irq(struct mp_chip_data *data, int apic, int pin)
@@ -385,13 +384,6 @@ static void __remove_pin_from_irq(struct mp_chip_data *data, int apic, int pin)
 		}
 }
 
-static void add_pin_to_irq_node(struct mp_chip_data *data,
-				int node, int apic, int pin)
-{
-	if (__add_pin_to_irq_node(data, node, apic, pin))
-		panic("IO-APIC: failed to add irq-pin. Can not proceed\n");
-}
-
 /*
  * Reroute an IRQ to a different pin.
  */
@@ -1000,8 +992,7 @@ static int alloc_isa_irq_from_domain(struct irq_domain *domain,
 	if (irq_data && irq_data->parent_data) {
 		if (!mp_check_pin_attr(irq, info))
 			return -EBUSY;
-		if (__add_pin_to_irq_node(irq_data->chip_data, node, ioapic,
-					  info->ioapic.pin))
+		if (!add_pin_to_irq_node(irq_data->chip_data, node, ioapic, info->ioapic.pin))
 			return -ENOMEM;
 	} else {
 		info->flags |= X86_IRQ_ALLOC_LEGACY;
@@ -3024,10 +3015,8 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 		return -ENOMEM;
 
 	ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, info);
-	if (ret < 0) {
-		kfree(data);
-		return ret;
-	}
+	if (ret < 0)
+		goto free_data;
 
 	INIT_LIST_HEAD(&data->irq_2_pin);
 	irq_data->hwirq = info->ioapic.pin;
@@ -3036,7 +3025,10 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 	irq_data->chip_data = data;
 	mp_irqdomain_get_attr(mp_pin_to_gsi(ioapic, pin), data, info);
 
-	add_pin_to_irq_node(data, ioapic_alloc_attr_node(info), ioapic, pin);
+	if (!add_pin_to_irq_node(data, ioapic_alloc_attr_node(info), ioapic, pin)) {
+		ret = -ENOMEM;
+		goto free_irqs;
+	}
 
 	mp_preconfigure_entry(data);
 	mp_register_handler(virq, data->is_level);
@@ -3051,6 +3043,12 @@ int mp_irqdomain_alloc(struct irq_domain *domain, unsigned int virq,
 		    ioapic, mpc_ioapic_id(ioapic), pin, virq,
 		    data->is_level, data->active_low);
 	return 0;
+
+free_irqs:
+	irq_domain_free_irqs_parent(domain, virq, nr_irqs);
+free_data:
+	kfree(data);
+	return ret;
 }
 
 void mp_irqdomain_free(struct irq_domain *domain, unsigned int virq,




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