Re: [PATCH] irqchip/gic-v5: Fix kmemleak L2 IST table entries false positives

[Marc Zyngier <maz@kernel.org>]

On Mon, 11 Aug 2025 14:50:01 +0100,
Lorenzo Pieralisi <lpieralisi@kernel.org> wrote:
> 
> L2 IST table entries are allocated with the kmalloc interface
> and their physical addresses are programmed in the GIC (either
> IST base address register or L1 IST table entries) but their
> virtual addresses are not stored in any kernel data structure
> because they are not needed at runtime - the L2 IST table entries
> are managed through system instructions but never dereferenced
> directly by the driver.
> 
> This triggers kmemleak false positive reports:
> 
> unreferenced object 0xffff00080039a000 (size 4096):
>   comm "swapper/0", pid 0, jiffies 4294892296
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace (crc 0):
>     kmemleak_alloc+0x34/0x40
>     __kmalloc_noprof+0x320/0x464
>     gicv5_irs_iste_alloc+0x1a4/0x484
>     gicv5_irq_lpi_domain_alloc+0xe4/0x194
>     irq_domain_alloc_irqs_parent+0x78/0xd8
>     gicv5_irq_ipi_domain_alloc+0x180/0x238
>     irq_domain_alloc_irqs_locked+0x238/0x7d4
>     __irq_domain_alloc_irqs+0x88/0x114
>     gicv5_of_init+0x284/0x37c
>     of_irq_init+0x3b8/0xb18
>     irqchip_init+0x18/0x40
>     init_IRQ+0x104/0x164
>     start_kernel+0x1a4/0x3d4
>     __primary_switched+0x8c/0x94
> 
> Instruct kmemleak to ignore L2 IST table memory allocation
> virtual addresses to prevent these false positive reports.
> 
> Reported-by: Jinjie Ruan <ruanjinjie@huawei.com>
> Closes: https://lore.kernel.org/lkml/cc611dda-d1e4-4793-9bb2-0eaa47277584@huawei.com/
> Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Marc Zyngier <maz@kernel.org>
> ---
>  drivers/irqchip/irq-gic-v5-irs.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/irqchip/irq-gic-v5-irs.c b/drivers/irqchip/irq-gic-v5-irs.c
> index ad1435a858a4..e8a576f66366 100644
> --- a/drivers/irqchip/irq-gic-v5-irs.c
> +++ b/drivers/irqchip/irq-gic-v5-irs.c
> @@ -5,6 +5,7 @@
>  
>  #define pr_fmt(fmt)	"GICv5 IRS: " fmt
>  
> +#include <linux/kmemleak.h>
>  #include <linux/log2.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> @@ -117,6 +118,7 @@ static int __init gicv5_irs_init_ist_linear(struct gicv5_irs_chip_data *irs_data
>  		kfree(ist);
>  		return ret;
>  	}
> +	kmemleak_ignore(ist);
>  
>  	return 0;
>  }
> @@ -232,6 +234,7 @@ int gicv5_irs_iste_alloc(const u32 lpi)
>  		kfree(l2ist);
>  		return ret;
>  	}
> +	kmemleak_ignore(l2ist);
>  
>  	/*
>  	 * Make sure we invalidate the cache line pulled before the IRS

Acked-by: Marc Zyngier <maz@kernel.org>

	M.

-- 
Without deviation from the norm, progress is not possible.