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[76.182.20.124]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6d3961ecdcbsm63623066d6.31.2024.11.11.12.19.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 Nov 2024 12:19:19 -0800 (PST) From: Josef Bacik To: kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, brauner@kernel.org, torvalds@linux-foundation.org, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Subject: [PATCH v6 07/17] fsnotify: generate pre-content permission event on truncate Date: Mon, 11 Nov 2024 15:17:56 -0500 Message-ID: <95769c056a65cbc2d6ca6aa1fb66918acbe5ad0e.1731355931.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 Generate FS_PRE_ACCESS event before truncate, without sb_writers held. Move the security hooks also before sb_start_write() to conform with other security hooks (e.g. in write, fallocate). The event will have a range info of the page surrounding the new size to provide an opportunity to fill the conetnt at the end of file before truncating to non-page aligned size. Signed-off-by: Amir Goldstein --- fs/open.c | 31 +++++++++++++++++++++---------- include/linux/fsnotify.h | 32 ++++++++++++++++++++++---------- 2 files changed, 43 insertions(+), 20 deletions(-) diff --git a/fs/open.c b/fs/open.c index c822f88d4c1d..51103ba339d0 100644 --- a/fs/open.c +++ b/fs/open.c @@ -81,14 +81,18 @@ long vfs_truncate(const struct path *path, loff_t length) if (!S_ISREG(inode->i_mode)) return -EINVAL; - error = mnt_want_write(path->mnt); - if (error) - goto out; - idmap = mnt_idmap(path->mnt); error = inode_permission(idmap, inode, MAY_WRITE); if (error) - goto mnt_drop_write_and_out; + return error; + + error = fsnotify_truncate_perm(path, length); + if (error) + return error; + + error = mnt_want_write(path->mnt); + if (error) + return error; error = -EPERM; if (IS_APPEND(inode)) @@ -114,7 +118,7 @@ long vfs_truncate(const struct path *path, loff_t length) put_write_access(inode); mnt_drop_write_and_out: mnt_drop_write(path->mnt); -out: + return error; } EXPORT_SYMBOL_GPL(vfs_truncate); @@ -175,11 +179,18 @@ long do_ftruncate(struct file *file, loff_t length, int small) /* Check IS_APPEND on real upper inode */ if (IS_APPEND(file_inode(file))) return -EPERM; - sb_start_write(inode->i_sb); + error = security_file_truncate(file); - if (!error) - error = do_truncate(file_mnt_idmap(file), dentry, length, - ATTR_MTIME | ATTR_CTIME, file); + if (error) + return error; + + error = fsnotify_truncate_perm(&file->f_path, length); + if (error) + return error; + + sb_start_write(inode->i_sb); + error = do_truncate(file_mnt_idmap(file), dentry, length, + ATTR_MTIME | ATTR_CTIME, file); sb_end_write(inode->i_sb); return error; diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 1e87a54b88b6..fbcdddb9601a 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -132,17 +132,14 @@ static inline int fsnotify_file(struct file *file, __u32 mask) } #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS -static inline int fsnotify_pre_content(const struct file *file, +static inline int fsnotify_pre_content(const struct path *path, const loff_t *ppos, size_t count) { - struct inode *inode = file_inode(file); + struct inode *inode = d_inode(path->dentry); struct file_range range; const void *data; int data_type; - if (file->f_mode & FMODE_NONOTIFY) - return 0; - /* * Pre-content events are only reported for regular files and dirs * if there are any pre-content event watchers on this sb. @@ -155,18 +152,17 @@ static inline int fsnotify_pre_content(const struct file *file, /* Report page aligned range only when pos is known */ if (ppos) { - range.path = &file->f_path; + range.path = path; range.pos = PAGE_ALIGN_DOWN(*ppos); range.count = PAGE_ALIGN(*ppos + count) - range.pos; data = ⦥ data_type = FSNOTIFY_EVENT_FILE_RANGE; } else { - data = &file->f_path; + data = path; data_type = FSNOTIFY_EVENT_PATH; } - return fsnotify_parent(file->f_path.dentry, FS_PRE_ACCESS, - data, data_type); + return fsnotify_parent(path->dentry, FS_PRE_ACCESS, data, data_type); } /* @@ -184,11 +180,14 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, */ lockdep_assert_once(file_write_not_started(file)); + if (file->f_mode & FMODE_NONOTIFY) + return 0; + /* * read()/write and other types of access generate pre-content events. */ if (perm_mask & (MAY_READ | MAY_WRITE | MAY_ACCESS | MAY_OPEN)) { - int ret = fsnotify_pre_content(file, ppos, count); + int ret = fsnotify_pre_content(&file->f_path, ppos, count); if (ret) return ret; @@ -204,6 +203,14 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, return fsnotify_file(file, FS_ACCESS_PERM); } +/* + * fsnotify_truncate_perm - permission hook before file truncate + */ +static inline int fsnotify_truncate_perm(const struct path *path, loff_t length) +{ + return fsnotify_pre_content(path, &length, 0); +} + /* * fsnotify_file_perm - permission hook before file access (unknown range) */ @@ -235,6 +242,11 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, return 0; } +static inline int fsnotify_truncate_perm(const struct path *path, loff_t length) +{ + return 0; +} + static inline int fsnotify_file_perm(struct file *file, int perm_mask) { return 0;