linux-kernel - Re: [PATCH] powerpc/mm: Fix null-pointer dereference in pgtable_cache

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Message-ID: <32077b74-7335-4f4d-8858-c53c820150d0@csgroup.eu>
Date:   Fri, 24 Nov 2023 15:17:27 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Kunwu Chan <chentao@...inos.cn>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "npiggin@...il.com" <npiggin@...il.com>
CC:     "kunwu.chan@...mail.com" <kunwu.chan@...mail.com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc/mm: Fix null-pointer dereference in
 pgtable_cache_add



Le 22/11/2023 à 10:00, Kunwu Chan a écrit :
> [Vous ne recevez pas souvent de courriers de chentao@...inos.cn. Découvrez pourquoi ceci est important à https://aka.ms/LearnAboutSenderIdentification ]
> 
> kasprintf() returns a pointer to dynamically allocated memory
> which can be NULL upon failure. Ensure the allocation was successful
> by checking the pointer validity.

Are you sure this is needed ? Did you check what happens what name is NULL ?

If I followed stuff correctly, I end up in function 
sysfs_do_create_link_sd() which already handles the NULL name case which 
a big hammer warning.

> 
> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
> ---
>   arch/powerpc/mm/init-common.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/arch/powerpc/mm/init-common.c b/arch/powerpc/mm/init-common.c
> index 119ef491f797..0884fc601c46 100644
> --- a/arch/powerpc/mm/init-common.c
> +++ b/arch/powerpc/mm/init-common.c
> @@ -139,6 +139,8 @@ void pgtable_cache_add(unsigned int shift)
> 
>          align = max_t(unsigned long, align, minalign);
>          name = kasprintf(GFP_KERNEL, "pgtable-2^%d", shift);
> +       if (!name)
> +               return;
>          new = kmem_cache_create(name, table_size, align, 0, ctor(shift));
>          if (!new)
>                  panic("Could not allocate pgtable cache for order %d", shift);
> --
> 2.34.1
>