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[76.182.20.124]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-45801b3277esm1506081cf.31.2024.09.04.13.29.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Sep 2024 13:29:18 -0700 (PDT) From: Josef Bacik To: kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, brauner@kernel.org, linux-xfs@vger.kernel.org, linux-bcachefs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v5 03/18] fsnotify: generate pre-content permission event on open Date: Wed, 4 Sep 2024 16:27:53 -0400 Message-ID: <4b235bf62c99f1f1196edc9da4258167314dc3c3.1725481503.git.josef@toxicpanda.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Amir Goldstein FS_PRE_ACCESS or FS_PRE_MODIFY will be generated on open depending on file open mode. The pre-content event will be generated in addition to FS_OPEN_PERM, but without sb_writers held and after file was truncated in case file was opened with O_CREAT and/or O_TRUNC. The event will have a range info of (0..0) to provide an opportunity to fill entire file content on open. Signed-off-by: Amir Goldstein Reviewed-by: Christian Brauner --- fs/namei.c | 9 +++++++++ include/linux/fsnotify.h | 10 +++++++++- 2 files changed, 18 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index 3a4c40e12f78..c16487e3742d 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -3735,6 +3735,15 @@ static int do_open(struct nameidata *nd, } if (do_truncate) mnt_drop_write(nd->path.mnt); + + /* + * This permission hook is different than fsnotify_open_perm() hook. + * This is a pre-content hook that is called without sb_writers held + * and after the file was truncated. + */ + if (!error) + error = fsnotify_file_perm(file, MAY_OPEN); + return error; } diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 7600a0c045ba..fb3837b8de4c 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -168,6 +168,10 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, fsnotify_mask = FS_PRE_MODIFY; else if (perm_mask & (MAY_READ | MAY_ACCESS)) fsnotify_mask = FS_PRE_ACCESS; + else if (perm_mask & MAY_OPEN && file->f_mode & FMODE_WRITER) + fsnotify_mask = FS_PRE_MODIFY; + else if (perm_mask & MAY_OPEN) + fsnotify_mask = FS_PRE_ACCESS; else return 0; @@ -176,10 +180,14 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, /* * fsnotify_file_perm - permission hook before file access + * + * Called from read()/write() with perm_mask MAY_READ/MAY_WRITE. + * Called from open() with MAY_OPEN without sb_writers held and after the file + * was truncated. Note that this is a different event from fsnotify_open_perm(). */ static inline int fsnotify_file_perm(struct file *file, int perm_mask) { - return fsnotify_file_area_perm(file, perm_mask, NULL, 0); + return fsnotify_file_area_perm(file, perm_mask, &file->f_pos, 0); } /*