[PATCH v2] irqdomain: Auto-set IRQ_DOMAIN_FLAG_DESTROY_GC in __irq_domain_instantiate()

[Qingshuang Fu]

When a driver uses irq_domain_instantiate() with dgc_info to create
generic irq chips, the domain is expected to automatically clean up
the generic chips when irq_domain_remove() is called. However,
__irq_domain_instantiate() does not set the IRQ_DOMAIN_FLAG_DESTROY_GC
flag which is required by irq_domain_remove() to trigger cleanup.

Currently all existing callers of irq_domain_instantiate() with dgc_info
manually set this flag, which is error-prone. If a future caller forgets to
set the flag, generic chips allocated by irq_domain_alloc_generic_chips()
will leak on domain removal.

Set IRQ_DOMAIN_FLAG_DESTROY_GC right after irq_domain_alloc_generic_chips()
succeeds inside __irq_domain_instantiate().

This makes automatic cleanup the default for all users that provide
dgc_info via irq_domain_instantiate().

This is the correct location for several reasons:
- irq_domain_instantiate() is a high-level wrapper which internally
  allocates the generic chips, so it should also take responsibility
  for arranging their cleanup.
- Automatically setting the flag inside irq_domain_alloc_generic_chips()
  would affect legacy callers like __irq_alloc_domain_generic_chips(),
  some of which perform custom manual cleanup and could hit use-after-free.

Fixes: e6f67ce32e8e ("irqdomain: Add support for generic irq chips creation before publishing a domain")
Signed-off-by: Qingshuang Fu <fuqingshuang@xxxxxxxxxx>
---
Changes in v2:
- Move setting of IRQ_DOMAIN_FLAG_DESTROY_GC from irq_domain_alloc_generic_chips()
  into the info->dgc_info branch inside __irq_domain_instantiate(), as suggested.
  This avoids unconditional flag-setting which could cause use-after-free for
  legacy drivers with custom generic chip cleanup paths.

 kernel/irq/irqdomain.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 57c819da30c2..4fdcb6df5306 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -344,6 +344,7 @@ static struct irq_domain *__irq_domain_instantiate(const struct irq_domain_info
 		err = irq_domain_alloc_generic_chips(domain, info->dgc_info);
 		if (err)
 			goto err_domain_free;
+		domain->flags |= IRQ_DOMAIN_FLAG_DESTROY_GC;
 	}
 
 	if (info->init) {

base-commit: a500db7819c50db59e55f1b4fa1c3baa5a2616f3
-- 
2.25.1