From 54b41388f58f1d2e640b5339e3745ee3e5f9affe Mon Sep 17 00:00:00 2001 From: Alessio Balsini Date: Tue, 27 Oct 2020 13:24:03 +0000 Subject: [PATCH] ANDROID: vfs: add d_canonical_path for stacked filesystem support Inotify does not currently know when a filesystem is acting as a wrapper around another fs. This means that inotify watchers will miss any modifications to the base file, as well as any made in a separate stacked fs that points to the same file. d_canonical_path solves this problem by allowing the fs to map a dentry to a path in the lower fs. Inotify can use it to find the appropriate place to watch to be informed of all changes to a file. Test: Pixel 4.19 Bug: 171780975 Change-Id: I09563baffad1711a045e45c1bd0bd8713c2cc0b6 Signed-off-by: Daniel Rosenberg [astrachan: Folded 34df4102216e ("ANDROID: fsnotify: Notify lower fs of open") into this patch] Signed-off-by: Alistair Strachan Signed-off-by: Yongqin Liu Signed-off-by: Alessio Balsini --- fs/notify/inotify/inotify_user.c | 16 ++++++++++++++-- include/linux/dcache.h | 3 ++- include/linux/fsnotify.h | 9 +++++++++ 3 files changed, 25 insertions(+), 3 deletions(-) diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c index 97a51690338e..9d220c72014a 100644 --- a/fs/notify/inotify/inotify_user.c +++ b/fs/notify/inotify/inotify_user.c @@ -702,6 +702,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, struct fsnotify_group *group; struct inode *inode; struct path path; + struct path alteredpath; + struct path *canonical_path = &path; struct fd f; int ret; unsigned flags = 0; @@ -747,13 +749,23 @@ SYSCALL_DEFINE3(inotify_add_watch, int, fd, const char __user *, pathname, if (ret) goto fput_and_out; + /* support stacked filesystems */ + if (path.dentry && path.dentry->d_op) { + if (path.dentry->d_op->d_canonical_path) { + path.dentry->d_op->d_canonical_path(&path, + &alteredpath); + canonical_path = &alteredpath; + path_put(&path); + } + } + /* inode held in place by reference to path; group by fget on fd */ - inode = path.dentry->d_inode; + inode = canonical_path->dentry->d_inode; group = f.file->private_data; /* create/update an inode mark */ ret = inotify_update_watch(group, inode, mask); - path_put(&path); + path_put(canonical_path); fput_and_out: fdput(f); return ret; diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 1c6bb25a8501..ee2d177dc0e8 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -151,7 +151,8 @@ struct dentry_operations { int (*d_manage)(const struct path *, bool); struct dentry *(*d_real)(struct dentry *, const struct inode *); - ANDROID_KABI_RESERVE(1); + ANDROID_KABI_USE(1, void (*d_canonical_path)(const struct path *, + struct path *)); ANDROID_KABI_RESERVE(2); ANDROID_KABI_RESERVE(3); ANDROID_KABI_RESERVE(4); diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index fd1ce10553bf..f3eb2b2e05f4 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -211,11 +211,20 @@ static inline void fsnotify_open(struct file *file) { const struct path *path = &file->f_path; struct inode *inode = file_inode(file); + struct path lower_path; __u32 mask = FS_OPEN; if (S_ISDIR(inode->i_mode)) mask |= FS_ISDIR; + if (path->dentry->d_op && path->dentry->d_op->d_canonical_path) { + path->dentry->d_op->d_canonical_path(path, &lower_path); + fsnotify_parent(&lower_path, NULL, mask); + fsnotify(lower_path.dentry->d_inode, mask, &lower_path, + FSNOTIFY_EVENT_PATH, NULL, 0); + path_put(&lower_path); + } + fsnotify_parent(path, NULL, mask); fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0); }