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[35.203.150.192]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-8a6a6cfa342sm1626775b3a.41.2026.10.28.16.14.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Oct 2026 16:14:01 -0700 (PDT) Date: Wed, 28 Oct 2026 23:13:57 +0000 From: David Matlack To: sashiko-reviews@lists.linux.dev Cc: kexec@lists.infradead.org, linux-mm@kvack.org, Alexander Graf , Andrew Morton , Baolin Wang , Christian Brauner , David Hildenbrand , Hugh Dickins , Jonathan Corbet , "Liam R. Howlett" , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Pasha Tatashin , Pratyush Yadav , Randy Dunlap , Samiullah Khawaja , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka Subject: Re: [PATCH v2 09/10] mm/shmem_luo: Allow retrieving tmpfs files with O_RDONLY Message-ID: References: <20261022225035.377445-1-dmatlack@google.com> <20261022225035.377445-10-dmatlack@google.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: DC89920003 X-Stat-Signature: 87fjic6kqod8zrhgmtpgj8m3h9y4dy1g X-Rspamd-Server: rspam06 X-Spam-Status: No, score=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793229244-746058 X-HE-Meta: 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 o6xsZadm t5de/rA57iWMQEuxbg5z8ITRHOQUr8VyjXLfw0/Ll+DxFsuioRDlx3gWfWbkCda5HuIM52ZU1cqMfpzpFEYMqld6lAg/T4LFHqR6eHuTA96s1U2onqmFlZiUVL8trDYCYM1WqEcNFBSAcBzFDTDPVZH4k5il+Z/eGcQ7d0P5v/fWHKDnwDOqpzuNKRqbPz92Akj5/WDPp7g48bOQSLJ2k78IMB9KFvwAU7oinOmauA4q8jhllDfUq5re8IsVCPsNLzhT1d7DQa9/mpz24iZRh76wMxZLWHtLcAWTcBQoFMMjoh2HkxcCRcEIoF9NjQwTUDnsifA+UkAKpe1rCRTL/IGlUx/MUa+K0nSnT3RrTPVdIu2+gZPYiRwqLryKv9VaXG8g99WPhKrgQeON6F8sqESHG6/oMc6GEnzACfu4ZnEfMmG8M6ce+eFblBg== 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 2026-10-23 10:51 PM, sashiko-bot@kernel.org wrote: > > + ro_file = dentry_open(&file->f_path, flags, current_cred()); > > + fput(file); > > + return ro_file; > > } > > > > static int shmem_luo_retrieve(struct liveupdate_file_op_args *args) > > [Severity: Medium] > When userspace retrieves a tmpfs file via LIVEUPDATE_SESSION_RETRIEVE_FD with > O_RDONLY in arg->flags, does passing the raw flags variable to dentry_open() > in shmem_luo_create_tmpfs_file() in mm/shmem_luo.c bypass the flag > normalization performed by file_open_root() -> build_open_flags()? > > In fs/open.c, build_open_flags() strips O_CLOEXEC and ensures O_DSYNC is set > when __O_SYNC is present: > > u64 flags = how->flags; > u64 strip = O_CLOEXEC; > ... > flags &= ~strip; > ... > if (flags & __O_SYNC) > flags |= O_DSYNC; > > Because dentry_open() -> alloc_empty_file() -> init_file() initializes > ro_file->f_flags directly from the passed flags and do_dentry_open() only > clears: > > f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | __O_REGULAR); > f->f_iocb_flags = iocb_flags(f); > > passing O_RDONLY | O_CLOEXEC in arg->flags leaves O_CLOEXEC in > ro_file->f_flags (visible via fcntl(fd, F_GETFL) and /proc//fdinfo/), > and passing O_RDONLY | __O_SYNC without O_DSYNC leaves O_DSYNC and IOCB_DSYNC > unset on ro_file. > > Should dentry_open() be passed (file->f_flags & ~O_ACCMODE) | O_RDONLY instead > of flags so that ro_file uses the normalized flags from file? Yes. I will fix this in v3 to re-open the read-only file with the flags that file_open_root() already normalized.