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Thu, 18 Jan 2024 04:23:15 -0800 (PST) MIME-Version: 1.0 References: <20240118110022.2538350-1-elver@google.com> In-Reply-To: From: Marco Elver Date: Thu, 18 Jan 2024 13:22:37 +0100 Message-ID: Subject: Re: [PATCH] mm, kmsan: fix infinite recursion due to RCU critical section To: Charan Teja Kalla Cc: Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzbot+93a9e8a3dea8d6085e12@syzkaller.appspotmail.com Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Stat-Signature: p96hurndex49rhfbjji1gazzmqfhqnhh X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 2DE2CC0014 X-HE-Tag: 1705580595-635204 X-HE-Meta: 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 HgwFJ4QQ /UxuHRrfxRQw8mvFuuS0dWhvRgo9l8DyVse03QufECzlKCcj8PtAXBHQLu1g+tdjUIX+aLR9iwZIvv7oTdSj/vMtDfzQ59yDHQ5XHDMaSlLA4iiS9LjROWf5MOp2Ur+Kd9h7yig3FxcRERliO0VkG2ZQqCUhYAk8WZY6LF8CzXzf/vGHxZuCGlaVFgPmktQZijhUzLw3jDCX+C6jCnimiZBIFe5RFRwknVHpARiCzetOKufXOT67PeUAk3gNfNGzkoMRM72uekuKBrlTpPdMWI1ZPXXOB7QcfYnZZXuX0AfzUBvZz+oBVNC4qo2O78UYwjSIlm3uLfpAlsdaVdRl9I5ApxtCH/xLlI36YRKdpvzxMTF1a1rDAnVk/t0eQsfXxl9nvryT/IuKZo8m/4GwMBvFn9Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000022, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 18 Jan 2024 at 12:28, Charan Teja Kalla wrote: > > May I ask if KMSAN also instruments the access to the memory managed as > ZONE_DEVICE. You know this is not the RAM and also these pages will > never be onlined thus also not be available in buddy. > > Reason for the ask is that this patch is introduced because of a race > between pfn walker ends up in pfn of zone device memory. > > If KMSAN never instruments this, does it look good to you to have the > KMSAN version of pfn_valid(), as being suggested by Alexander in the > other mail. It would be nice to avoid duplicating functions - both options have downsides: 1. Shared pfn_valid(): it might break for KMSAN again in future if new recursion is introduced. 2. KMSAN-version of pfn_valid(): it might break if pfn_valid() changes in future. I suspect #1 is less likely. What is your main concern by switching to rcu_read_lock_sched()?