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h=Date:From:To:Cc:Subject:References:In-Reply-To; b=i5V4VCQrdHU+uG2pJYqRPhqkSzGsM4xSLU1XJ0z+Tn+sGBvGl6PS5AjTKVdmcv7K9 UfzYyrhEX+CTogKDpTIY8lSfX1ObveUxmAkok+oz+mpAYPvI8fHZHyt0umP7bvrRHs BeNRToBTnOZoQW8aS/ryia3YZ/4UTSkJso5hJLv3xJLZ2C51/dd1tulN+/RHimZul7 DiXbkdNPUq/Nv5Ktmq35EoqixXG6MoyeZZg4wNF0PxRH4sBVkkbdL3yOv4vcKZi4tz BpWuka+s9hoS3MQ0yrRcYrO7hYd8o7kThsrGemf08Ua37ljn+RT6XbUviQ0AeCcBh0 YvlSe4qWWm1Sw== Date: Mon, 26 Oct 2026 13:39:39 +0000 From: "Lorenzo Stoakes (ARM)" To: "David Hildenbrand (Arm)" Cc: Andrew Morton , Ngoc Quy , liam@infradead.org, Vlastimil Babka , Jann Horn , Pedro Falcato , Muhammad Usama Anjum , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/task_mmu: pin mm_users in do_pagemap_scan() Message-ID: References: <20261014095540.3261469-1-ngocquy0700@gmail.com> <20261019174659.42c3529d5e35563cc6e5244c@linux-foundation.org> <9aa49812-1132-458e-9bf5-6dba8b476b26@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9aa49812-1132-458e-9bf5-6dba8b476b26@kernel.org> X-Stat-Signature: 9fr7wspjupkhqonqhppre3ekmngxedbx X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5EF37180005 X-Rspam-User: X-HE-Tag: 1793021985-73578 X-HE-Meta: U2FsdGVkX1/aRyshykUPKZ4VL07ZAN0UH457ON7QhwwPy8PC9YjKMogOEyvAKLp03IKwn8FPVwm+oYv0fgfv0IuMlwcVFgsqyWtWRiyyBbD0BPkp9tVvYCOm8ly6CgzOlZyuzg/TbZMZqrzDu3zgQ1T5mWoHAyPA/c5KgLSs8YoiN/fmecm7np2aBxpYVqKFmA2wP9/6BqHCK3MoRXS91kP2k39Ep69dazJnpbWLo8M1UVsqC6ybcoW7S5Onzc9yPBh1FpolysjBWFarc0FCcFmbuOetrQCI2x9+Grjf0j2m4K4VM/WQ4V/v+wPzmJUz3/W1W/qBV4ssxDf4BUUgaB3e2A9ihjbr1Q7L8/4CfZYNNdNIZG4gy7pSZxswC1UpaqccL3oVTXUv75YRwVJD4QpPLLo7sEkNDeMvUJgSTNxHAVWvldWtJccJpKs05sM9BRfiMBbdpF+He/YcwR0odq7EDK5iHKXiW/z2YJp3H4MirNnE2FvFUObNFZb9noG6oR7wGdEOpCp9ZkO8aCpA3m531PDf4q06mjRVklR3geVy2NsX/QrqZk+BIVbP2kaQ/0YAs9WShHzoJb2zIuRDhtQF8eeEnpSdSqsSUMC2JQZ2RUccx6ydf+ka7/4/kN10/uwR5OfU5kAKWjHCQ74kbhWH3HuD7VSPgHhIEXhInERufjqNr3npxoJIplaCOaVaHvifBWNXB9XXjJmdLc7QpWFpneWSRrUQoMPVYIWko+Keg+1KpC1mL93QYvBxN3dVFp5EfBhdk2ig6zSFwX8H3iFj74a8m77dwIfR4Gr2HnAoXDKvJEsjrHbYsnBRVmNbyBJpawyHCu/hZMx4t5DqrhU2P446xaPBpkTqfDLkVAcVsq5YGSVbq6zONSzAWsBlhpkMghqBoqRQeVWj26VXaF7dMM9ga9dERZsQjA/rZdLbvSba9k1V95lYIkVz3ySC8m6sGiRmyGaBGxl4sO/ f/hk3ntf 6d4AHj0DlY9utiuOUCwk7LMKhlPgO7LWnwoX4MKK990pDXBnwkJL9CuWunlFbRYFX3nOB/bItR2ZIO5kNRvLHxV1xCvh9+U0Y5pToqXZ1g+T8TnC2E0MlLDdwxj+u6wKHsUVGh4Lh7XKCdXfOgEF2prqVRFsuUb9Ul8+iYCaGb749rU/GaFyaw+uFQXvMZ7QjGen1X9HKGMadpBM3evXeN7UGNBt3csSXBcbps2FOtl2E5qkSTRn6DU2gi4ql5B/5O6RvG117Cg3O0TXAF1XQQUdIeEFzqEvfuz05Fg14SbvT7bQ= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sun, Oct 25, 2026 at 11:55:59AM +0100, David Hildenbrand (Arm) wrote: > On 10/20/26 02:46, Andrew Morton wrote: > > All looks good and checks out for me, thanks. > > > > Except... > > > >> --- a/fs/proc/task_mmu.c > >> +++ b/fs/proc/task_mmu.c > >> @@ -3231,15 +3231,18 @@ static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg) > >> size_t n_ranges_out = 0; > >> int ret; > >> > >> + if (!mm || !mmget_not_zero(mm)) > >> + return -ESRCH; > > > > Why the new test for !mm? The current call chain guarantees this is a > > cant-happen and the current do_pagemap_scan will cheerfully oops if > > mm==NULL. > > I'd just keep it for consistency with all the other checks in this file? Agreed. -- Cheers, Lorenzo