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bh=SkFG+3LyiNgprdYnBxxoNAJ5LTWjyrCvcaBrBUygRPY=; b=k8QvJEVPLl3+Wnza5ucCf/q5ANPBsfsS5q2DsJazrbN/aQ8GVelHKbK4ljsXFsEaww8Js+ Gx7b2Hn1SweS9x4S8glDkXjTavztLwL96TRRLXUuJ9rsSfDwkSOM2RdBa6698Y829n8qnK AiXQhF6e2HmfsUhzqkdpNhUImJQLZ2i4ouS2jqhEbzPN4qfA2gaqwd0/KziCTuD/++NdG4 JgGEuZjk60LgGg59Wcy4m680dMYCJRJX4RM26uaBpcAqnR+GC2r9E71oFe0Cjiz3uM9oEI JJCa29KRCm1VIfzjEgfggasJ+Pc6Y3IvA21xFg+gMlIzq2agfq7gaIZ45n3U/Q== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1697202933; 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=SkFG+3LyiNgprdYnBxxoNAJ5LTWjyrCvcaBrBUygRPY=; b=nQ8Tz2nlT9mL2M40ty37s55aeQyrJjiWyBvPdOrgzP9V4Ph06yuoCq3iOEqG6Fd1nmHWN9 bBa7RwJVhYSJapAQ== To: Andrzej Hajda , linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-mm@kvack.org Cc: Andrzej Hajda , Andi Shyti , Nirmoy Das , Janusz Krzysztofik Subject: Re: [PATCH v2] debugobjects: stop accessing objects after releasing spinlock In-Reply-To: <20230925131359.2948827-1-andrzej.hajda@intel.com> References: <20230925131359.2948827-1-andrzej.hajda@intel.com> Date: Fri, 13 Oct 2023 15:15:33 +0200 Message-ID: <87v8bak6iy.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 3968980024 X-Rspam-User: X-Stat-Signature: upsmjdc1ktdr5swnwgyakjnd9wppszuc X-Rspamd-Server: rspam01 X-HE-Tag: 1697202935-525063 X-HE-Meta: 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 EvTT7pqL XZN7S2tGd5aPKP101B2ZeXzY+o5qcT6XXtQF+7bRnZLcfdJU= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000010, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Sep 25 2023 at 15:13, Andrzej Hajda wrote: > After spinlock release object can be modified/freed by concurrent thread. > Using it in such case is error prone, even for printing object state. It cannot be freed. If that happens then the calling code will have an UAF problem on the tracked item too. If there is a concurrent modification then again, the calling code is lacking serialization on the tracked object. debugobject fundamentally relies on the call site being consistent simply because it _cannot_ invoke the fixup callbacks with the hash bucket lock held. What's the actualy problem you are trying to solve here. The changelog does not explain anything except of handwaving about modified/freed. Thanks, tglx