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b=FjBhwON2lGqcDeAsQsur5YQJpwijTGL4gNxeB5JDtzunt2ZZduk4xjYTAo4go/lcZ 2Ve+e21JhrcXXcs9OOlnbwi4MzsFVfRdSI1sHTUueXGDCH21vG3mBKNGGZpOdr7YlY cUViZLTP8txseKSOJ0MNjl+SB3FDOhv3ilrjaaXLxzb5OtnypOzQI+/hseFVUmFuvx biJmLnh3FuzD56tP9s1isiBSqoSCE9HED5vpgGDUK1LVc4GQj6oxVJ7kV8SfEJxucz GdAirjMlWMjzqoqiTgccW04NJAFGnOvGT/IILN4tjOafVrcHPqZHTHDWVgJyVSxIlT KbIcgx6+lz/Rw== Date: Mon, 26 Oct 2026 13:53:23 +0000 From: "Lorenzo Stoakes (ARM)" To: Hengyu Liang Cc: akpm@linux-foundation.org, linux-mm@kvack.org, liam@infradead.org, vbabka@kernel.org, jannh@google.com, pfalcato@suse.de, usama.anjum@arm.com, avagin@gmail.com, mirq-linux@rere.qmqm.pl, arnd@arndb.de, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] fs/proc/task_mmu: return -ENOTTY for unknown pagemap ioctls Message-ID: References: <20261023181300.3366487-1-hengyul@cs.unc.edu> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261023181300.3366487-1-hengyul@cs.unc.edu> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: ECA80C000B 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_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Stat-Signature: 5g9ojsdgrn97dhf1t6um95q6hi9fmuuy X-HE-Tag: 1793022809-763420 X-HE-Meta: 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 9FP+Xp77 hnI5VfM97t+OUKtM/OmFBOfG12iNK33Y7whyxGV1vTPeMiuILaL/dCN0Xvky9QLxDft/XbZ0efYs6raHpFyAyZ9HZqHqZ7znQIZelNCGYDGPwmmKLsZ80vgIXDZXhxB+kJmgwzoa3z4V9mnJSEuezCLvKk7B9FCY9qc+Cw3/dpkIZ+55QuwtZBfywh5vNjo4SBDZQZdd6MmSMTXlw08+92G2soGqUxQX70RsiV8qv7TKzHLeUGfoWabkqwRiA23yM5WKx++sdfz+r2KTXTlbeOUOe64H2PWZvoe5A06kLyL9NXNAmndceiuT8sqG/yIzWOghc 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 Fri, Oct 23, 2026 at 02:13:00PM -0400, Hengyu Liang wrote: > Commit 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and > optionally clear info about PTEs") made do_pagemap_cmd() the ioctl > handler of /proc//pagemap. > > However, do_pagemap_cmd() returns -EINVAL for every command other than > PAGEMAP_SCAN. Before that commit, pagemap had no ioctl handler, and > the VFS returned -ENOTTY for these commands. As of now, they fail with > EINVAL, so tcgetattr() and isatty() on pagemap report EINVAL instead > of ENOTTY. > > The issue can be reproduced with a simple C program: > > #include > #include > #include > > int main(void) > { > struct termios t; > int fd = open("/proc/self/pagemap", O_RDONLY); > > if (tcgetattr(fd, &t) < 0) > perror("tcgetattr"); > return 0; > } > > Before that commit, the result is: > > tcgetattr: Inappropriate ioctl for device > > After that commit, the result is: > > tcgetattr: Invalid argument > > This patch will return -ENOIOCTLCMD for unknown commands, as > procfs_procmap_ioctl() in the same file does, so that the VFS turns it > into -ENOTTY. > > Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs") > Cc: stable@vger.kernel.org > Signed-off-by: Hengyu Liang Seems reasonable, though I doubt any sane user is relying on this. Confirmed the conversion from -ENOIOCTLCMD (first time I saw that :) to -ENOTTY also. Reviewed-by: Lorenzo Stoakes (ARM) -- Cheers, Lorenzo