Re: [PATCH] powerpc/smp: Handle of_property_count_u32_elems() error in parse_thread_groups()

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Hi Nathan. Thanks for the fix.

On 11/9/26 11:30 PM, Nathan Chancellor wrote:
> After commit 0af298e62e5c ("treewide: refresh kmalloc_obj()
> conversions"), there is a warning on boot for several PowerPC
> configurations in QEMU:
> 
>    WARNING: mm/slub.c:5459 at ___kmalloc_large_node+0x174/0x1b0, CPU#0: swapper/0/1
>    Modules linked in:
>    CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.4.0-rc1-00262-g0af298e62e5c #1 PREEMPT(lazy)
>    NIP [c0000000006074e4] ___kmalloc_large_node+0x174/0x1b0
>    LR [c00000000060782c] __kmalloc_large_node_noprof+0x3c/0x150
>    Call Trace:
>    ...
>    [c00000000369fb60] [c000000000614ff0] __kmalloc_noprof+0x490/0x690
>    [c00000000369fbe0] [c000000000051308] _kzalloc_noprof.constprop.0+0x1c/0x74
>    [c00000000369fc00] [c00000000200b450] init_thread_group_cache_map+0xc0/0x2c4
>    ...
> 
> In this case, of_property_count_u32_elems() returns -EINVAL because
> there is no "ibm,thread-groups" property. When kcalloc() was used to
> allocate thread_group_array, the multiplication overflow check in
> _kmalloc_array_noprof() caught that a really large allocation was
> requested (as -EINVAL was converted to size_t) and returned NULL.
> kzalloc_objs() has no such check, so the large allocation check in
> __kmalloc_large_noprof() triggers the visible warning above.
> 
> Check if of_property_count_u32_elems() has returned an error and bail
> out if so, clearing up the warning.
> 
> Fixes: 790a1662d3a2 ("powerpc/smp: Parse ibm,thread-groups with multiple properties")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Looks fine to me.
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>

> ---
>   arch/powerpc/kernel/smp.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 7a25eaa59e62..58824f5f4c80 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -824,6 +824,8 @@ static int parse_thread_groups(struct device_node *dn,
>   	int i = 0;
>   
>   	count = of_property_count_u32_elems(dn, "ibm,thread-groups");
> +	if (count < 0)
> +		return count;
>   	thread_group_array = kzalloc_objs(u32, count);
>   	if (!thread_group_array)
>   		return -ENOMEM;
> 
> ---
> base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb
> base-tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> change-id: 20261109-powerpc-smp-handle-count-err-b48b9ffd6e90
> 
> Best regards,
> --
> Cheers,
> Nathan
> 

Should the similar fix is needed here as well?

arch/powerpc/platforms/powernv/idle.c:
         nr_idle_states = of_property_count_u32_elems(np,
                                                 "ibm,cpu-idle-state-flags");

         pnv_idle_states = kzalloc_objs(*pnv_idle_states, nr_idle_states);
         temp_u32 = kzalloc_objs(u32, nr_idle_states);
         temp_u64 = kzalloc_objs(u64, nr_idle_states);
         temp_string = kcalloc(nr_idle_states, sizeof(char *),  GFP_KERNEL);