linux-kernel - Re: [PATCH] pstore/zone: Use GFP

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Message-ID: <202209061315.08B5962@keescook>
Date:   Tue, 6 Sep 2022 13:18:57 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Qiujun Huang <hqjagain@...il.com>
Cc:     WeiXiong Liao <gmpy.liaowx@...il.com>, anton@...msg.org,
        ccross@...roid.com, tony.luck@...el.com,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore/zone: Use GFP_ATOMIC to allocate zone buffer

On Sun, Sep 04, 2022 at 11:17:13PM +0800, Qiujun Huang wrote:
> There is a case found when triggering a panic_on_oom, pstore fails to dump
> kmsg. Because psz_kmsg_write_record can't get the new buffer.
> 
> Handle this by using GFP_ATOMIC to allocate a buffer at lower watermark.
> 
> Signed-off-by: Qiujun Huang <hqjagain@...il.com>
> ---
>  fs/pstore/zone.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
> index 017d0d4ad329..2770746bb7aa 100644
> --- a/fs/pstore/zone.c
> +++ b/fs/pstore/zone.c
> @@ -761,7 +761,7 @@ static inline int notrace
> psz_kmsg_write_record(struct psz_context *cxt,
>   /* avoid destroying old data, allocate a new one */
>   len = zone->buffer_size + sizeof(*zone->buffer);
>   zone->oldbuf = zone->buffer;
> - zone->buffer = kzalloc(len, GFP_KERNEL);
> + zone->buffer = kzalloc(len, GFP_ATOMIC);
>   if (!zone->buffer) {
>   zone->buffer = zone->oldbuf;
>   return -ENOMEM;

This patch appears to be whitespace damaged, but I've manually applied
it. Thank you!

https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/commit/?h=for-next/pstore&id=27001e611bb642287eddf93227bd72d295a35453

-- 
Kees Cook