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d=linutronix.de; s=2020e; t=1602755983; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PlevN6yVm2HnwK034FXsfndh/959DVQqNZzufhIKA04=; b=z7V9dWcnjheORrqANNNbcItCw4NhNMjaxJ1idCJ71t24jY3QPie81gGDA7E7nctNIdESAb 3zo7jyQ72+1K7TCQ== To: Sergey Senozhatsky , Petr Mladek Cc: 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 In-Reply-To: <20201015063137.GA3668@jagdpanzerIV.localdomain> References: <20201014140514.GB17231@alley> <20201014151311.GB13775@alley> <20201014175051.GC13775@alley> <20201015063137.GA3668@jagdpanzerIV.localdomain> Date: Thu, 15 Oct 2020 12:05:42 +0206 Message-ID: <875z7bhks1.fsf@jogness.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain 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 2020-10-15, Sergey Senozhatsky 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. Indeed. I don't know how we missed that one. :-/ Reviewed-by: John Ogness