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Tue, 2 May 2023 19:13:50 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Message-ID: <237a9064-78bb-1fe9-4293-1409a705d2d1@I-love.SAKURA.ne.jp> Date: Tue, 2 May 2023 19:13:43 +0900 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2) From: Tetsuo Handa To: linux-fsdevel , Alexander Viro Cc: akpm@linux-foundation.org, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, syzbot , Dmitry Vyukov References: <0000000000007337c705fa1060e2@google.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E0BAA1A116C X-Stat-Signature: amjh3es9i9hu5q3rxxncaw81c9uh5aes X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1683029663-541983 X-HE-Meta: U2FsdGVkX1/JcZWdpLTWKN0x2VgkHee0T3jFUYpcF4xA5mJKfeXk2vNE1iBdtvZIHz74y2IJr4dk0ijZhs4f5O5t/BelbvcY8s/mXUeGsr8UqvA/0/wLkcprLonAe1bQTqUpw4ndek3fwp4LpRzyxchDHPS6xb+e8xQqht+E75hiGCYNw1nasZh6/KGOA1mIWfd2tpkBWZZyWaTWRMz97jvFHsCQHUiZEtLL5U6FjqdIrZYIG1id0t8ES1nCLTv0D2aNWmfBj5+SlZU1RTqICKRQsorEGQY6shbJcOP0k7nRZzG6HDbCbBb5Vbv/GUTKA7iof+9bjaQ/Bfig+htMI5a1d6PF+uv3j0xecEFySD4/zvsCPEPlAdDI0k8Xg1mnkpl/bvyoRuOfE169vP8c6MppTzR0uwcAelgIjXDdUHTidtESQgXU97HLLZzDEDt0MtHXS+VhjgsM+Awy8RDofb9Owoysjj81Kms+bCd5/d53uBuvn4LcM5tUuXyswdgpZb6RKdZWnRbexKvNuR+qkZ5fH108eE/7eEDcxDD9S6cKyUJaq+N5kQZ3Dj5uUYWLElKo5w78sHPK5sZ+MhjOmn0MEwbLoF/SxortdKZOwJ66ygdSNUu8rLSmG2PjMmkjuUOJcyWLduuu5+7ar41uZP6J32RjDsnglbLLRYPSW/1w8ZdeEFM/cMnS5aNSSJfDmN3IX4fBus+AW2iwbLESbyzF2zVGBbdhY2yp5JDqtnlSWhXr3dFpa1ni46adgKr6QxHcjA/kPmK+gC81QGamM8tyqJlQ+tgHw6UWtpKLA3j32ubAlI1y+QA5M48f3iFPgDle5xM2YGsrX/nW491GMtxk4WJ0S7IMs+UZhHTGRoYoLzG6iijCBP6K9GcBN4Gq+MU3nr5sJTsCgCIVV+aYscnosUU7H+qwDAKoykwnAuUUTgogTFRnqysmyGtzDWPfmC5LwPWqNDGTpGwOMYE nPAc9k3G y64AJ+LAzHeqslRIPxpp2Kqd/Kg== 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 2023/05/01 23:05, Tetsuo Handa wrote: >> Also, there was a similar report on updating i_{ctime,mtime} to current_time() >> which means that i_size is not the only field that is causing data race. >> https://syzkaller.appspot.com/bug?id=067d40ab9ab23a6fa0a8156857ed54e295062a29 > > Do we want to as well wrap i_{ctime,mtime} using data_race() ? > I think we need to use inode_lock_shared()/inode_unlock_shared() when calling generic_fillattr(), for i_{ctime,mtime} (128bits) are too large to copy atomically. Is it safe to call inode_lock_shared()/inode_unlock_shared() from generic_fillattr()? Is some filesystem already holding inode lock before calling generic_fillattr()?