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Wed, 14 Oct 2020 23:31:40 -0700 (PDT) Date: Thu, 15 Oct 2020 15:31:37 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: John Ogness , Sergey Senozhatsky , Steven Rostedt , Linux-Next Mailing List , linux-mm , open list , lkft-triage@lists.linaro.org, LTP List , Andrew Morton , Mike Rapoport , Stephen Rothwell , Rasmus Villemoes , Linus Torvalds , Greg Kroah-Hartman , Thomas Gleixner , Naresh Kamboju Subject: Re: [PATCH] printk: ringbuffer: Wrong data pointer when appending small string Message-ID: <20201015063137.GA3668@jagdpanzerIV.localdomain> References: <20201014140514.GB17231@alley> <20201014151311.GB13775@alley> <20201014175051.GC13775@alley> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201014175051.GC13775@alley> X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (20/10/14 19:50), Petr Mladek wrote: > diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c > index 2493348a1631..24a960a89aa8 100644 > --- a/kernel/printk/printk_ringbuffer.c > +++ b/kernel/printk/printk_ringbuffer.c > @@ -1125,7 +1125,10 @@ static char *data_realloc(struct printk_ringbuffer *rb, > > /* If the data block does not increase, there is nothing to do. */ > if (head_lpos - next_lpos < DATA_SIZE(data_ring)) { > - blk = to_block(data_ring, blk_lpos->begin); > + if (wrapped) > + blk = to_block(data_ring, 0); > + else > + blk = to_block(data_ring, blk_lpos->begin); > return &blk->data[0]; > } Great catch. Acked-by: Sergey Senozhatsky -ss