[PATCH] sh: intc: sort the prio and sense lists after filling them

[Karl Mehltretter <kmehltretter@gmail.com>]

register_intc_controller() sorts d->prio and d->sense right after
allocating them, with hw->nr_prio_regs and hw->nr_sense_regs as the
element count. The lists hold hw->nr_vectors entries and are only
filled later, by intc_register_irq().

On SH7785, sh7785-irq0123 and sh7785-irq4567 have four vectors but the
SoC's eleven priority registers, so sort() swaps 88 bytes in a 32 byte
kmalloc object at boot. slub_debug=FZPU reports "Right Redzone
overwritten" in kmalloc-32, and v6.5 and v6.6 panic in
__kmem_cache_alloc_node() while registering sh7785-irq0123.

Found with a custom QEMU model of the SH7785LCR. On it, v6.4
sh7785lcr_defconfig boots with SLAB, the defconfig default before v6.5,
and hangs before the console is up when built with SLUB.

Sort the lists once all vectors are registered, with the number of
entries that were added.

Fixes: b59f9f9775e6 ("sh: intc: optimize intc IRQ lookup")
Cc: stable@vger.kernel.org
Assisted-by: LLM
Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
---

Notes:
    Testing, all in QEMU on a custom SH7785LCR model, not on hardware:
    - v6.5 and v6.6 sh7785lcr_defconfig hang before the console is up
      (gcc 8 and gcc 14). With slub_debug=FZPU they boot and validating
      kmalloc-32 reports "Right Redzone overwritten" after the object
      holding the entries of sh7785-irq4567. With this patch they boot
      and the report is gone.
    - v6.4 sh7785lcr_defconfig (SLAB) boots. The same v6.4 built with SLUB
      hangs, reports the overflow with slub_debug=FZPU, and boots with
      this patch.
    - Current mainline boots with or without the patch, but reports the
      overflow with slub_debug=FZPU unless patched.
    Testing on real hardware is welcome.

 drivers/sh/intc/core.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/sh/intc/core.c b/drivers/sh/intc/core.c
index aa68fe190865d..ffbe60234eefc 100644
--- a/drivers/sh/intc/core.c
+++ b/drivers/sh/intc/core.c
@@ -275,9 +275,6 @@ int __init register_intc_controller(struct intc_desc *desc)
 			k += save_reg(d, k, hw->prio_regs[i].set_reg, smp);
 			k += save_reg(d, k, hw->prio_regs[i].clr_reg, smp);
 		}
-
-		sort(d->prio, hw->nr_prio_regs, sizeof(*d->prio),
-		     intc_handle_int_cmp, NULL);
 	}
 
 	if (hw->sense_regs) {
@@ -287,9 +284,6 @@ int __init register_intc_controller(struct intc_desc *desc)
 
 		for (i = 0; i < hw->nr_sense_regs; i++)
 			k += save_reg(d, k, hw->sense_regs[i].reg, 0);
-
-		sort(d->sense, hw->nr_sense_regs, sizeof(*d->sense),
-		     intc_handle_int_cmp, NULL);
 	}
 
 	if (hw->subgroups)
@@ -357,6 +351,11 @@ int __init register_intc_controller(struct intc_desc *desc)
 		}
 	}
 
+	sort(d->prio, d->nr_prio, sizeof(*d->prio),
+	     intc_handle_int_cmp, NULL);
+	sort(d->sense, d->nr_sense, sizeof(*d->sense),
+	     intc_handle_int_cmp, NULL);
+
 	intc_subgroup_init(desc, d);
 
 	/* enable bits matching force_enable after registering irqs */
-- 
2.53.0