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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678914318; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=IwGhmwR58ADGQ+ITIo7v6jnjt7oIvun400KU/kpOQR4=; b=J8CAyhxbNQd3Fut6TJFV5I4amFjdqbs7yampVQmwFv+XxXX3UT7UB62Hhb0sTaaofk CgVU21u4br3+6IIEwLraqBAZj3ZAZ0ocuoluChisI4ERwO3k+7hL1AHyZT6PzAdQFm37 EZWEQVH3ao16SWfITO3zvrGCTTHhYlAcu6GHx5ckr20Z+7qoArwnY2pt1QtVRo6UtuIB /Ss1JoDlNJ1nksjcVXDx3o2xVU70D1kh6AF7yc8pYqwABZJgQs8ol1ZktBpjd9e0s34V /m5t+xn1XJlRZMHq3MBJobUtEvdz6v/7i/N47yfoLv0jY4TkvvtBtc3vxuEmdnq6lJAz PHhg== X-Gm-Message-State: AO0yUKUscfW7HQhVHjYdePYF06aFROMBI4rL4kCxj1y9ObLdG2DjEk2P OnbhxXqXKTf2k8vpMJAsekYRtX2LAEjf32jNp1EyJA== X-Google-Smtp-Source: AK7set/O/C/AmSPYxARwLjtbc8HQkBpIBl2PZeSCG4mpPndRBaBsslTRMqibTUEyoa/Dpk4ISb2xZMwqOaEvshNFNg4= X-Received: by 2002:a6b:ed02:0:b0:74c:8243:9291 with SMTP id n2-20020a6bed02000000b0074c82439291mr19019902iog.1.1678914317895; Wed, 15 Mar 2023 14:05:17 -0700 (PDT) MIME-Version: 1.0 References: <20230315034441.44321-1-songmuchun@bytedance.com> <20230315125425.70a22d32cf46b23d249775ec@linux-foundation.org> In-Reply-To: <20230315125425.70a22d32cf46b23d249775ec@linux-foundation.org> From: Marco Elver Date: Wed, 15 Mar 2023 22:04:33 +0100 Message-ID: Subject: Re: [PATCH] mm: kfence: fix using kfence_metadata without initialization in show_object() To: Andrew Morton Cc: Muchun Song , glider@google.com, dvyukov@google.com, jannh@google.com, sjpark@amazon.de, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, muchun.song@linux.dev Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: D5281A001E X-Stat-Signature: arq8ytxdmkzwgk1wjdydurk8dp556hcz X-HE-Tag: 1678914318-498475 X-HE-Meta: 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 lQAst4mI Ej3nFI28BfvqDhRZ5Ox3x/cLQqJFhO8kIlhY5sWj2a8Jz8CIIVP/zCqYNtVXwg3fBBjEpwj1YGPfgQRRnzeMds6L68fN/gC8fkkc4wJ0z+QEZJXRTOxZuZ7tr/RWciKzBjP2z1dz34OjMyxGdrJzHweSV+8nfX2y0RQy4Ejxd3heAdR51BHAdtRN8tfURDQNzHz0vn/3DBAdrxsaIkyozboHqS74fFQUTmlL2Ss0DXBjqEVFSEJJN8/QoHtO/OynI88Nenqp10JLBbJHASRUS7BBTTWxbp7bOxLZiCcnpHCcEAmvYjv3XaovRn7PMKgIGQ8/v3nE859NbuO3v2gd81R06KkYAbVjc4HBcA28dKNSy83uXB1AxGP7V602CTc/VTbkqcZhj3/85w5BG9SwZuRPb3FmNYvafNResyEwh+XtVTic= 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 Wed, 15 Mar 2023 at 20:54, Andrew Morton wrote: > > On Wed, 15 Mar 2023 09:07:40 +0100 Marco Elver wrote: > > > On Wed, 15 Mar 2023 at 04:45, Muchun Song wrote: > > > > > > The variable kfence_metadata is initialized in kfence_init_pool(), then, it is > > > not initialized if kfence is disabled after booting. In this case, kfence_metadata > > > will be used (e.g. ->lock and ->state fields) without initialization when reading > > > /sys/kernel/debug/kfence/objects. There will be a warning if you enable > > > CONFIG_DEBUG_SPINLOCK. Fix it by creating debugfs files when necessary. > > > > > > Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") > > > Signed-off-by: Muchun Song > > > > Tested-by: Marco Elver > > Reviewed-by: Marco Elver > > Thanks, I'll add cc:stable to this. > > I assume the warning is the only known adverse effect of this bug? For architectures where the initial spinlock state is 0, the warning is the only issue. For architectures where that's not the case, it might result in lockup of the task querying the 'objects' file -- which isn't the case for any arch that supports KFENCE by the looks of it (last I checked 'sh' and 'parisc' don't support KFENCE). Thanks, -- Marco