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

[Ritesh Harjani (IBM) <ritesh.list@gmail.com>]

Nathan Chancellor <nathan@kernel.org> writes:

> 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>
> ---
>  arch/powerpc/kernel/smp.c | 2 ++
>  1 file changed, 2 insertions(+)


Thanks for fixing it. Looks good to me. Please feel free to add:

Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>