From 4bacc9c9234c7c8eec44f5ed4e960d9f96fa0f01 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 18 Jun 2015 14:32:31 +0100 Subject: overlayfs: Make f_path always point to the overlay and f_inode to the underlay Make file->f_path always point to the overlay dentry so that the path in /proc/pid/fd is correct and to ensure that label-based LSMs have access to the overlay as well as the underlay (path-based LSMs probably don't need it). Using my union testsuite to set things up, before the patch I see: [root@andromeda union-testsuite]# bash 5 /a/foo107 [root@andromeda union-testsuite]# stat /mnt/a/foo107 ... Device: 23h/35d Inode: 13381 Links: 1 ... [root@andromeda union-testsuite]# stat -L /proc/$$/fd/5 ... Device: 23h/35d Inode: 13381 Links: 1 ... After the patch: [root@andromeda union-testsuite]# bash 5 /mnt/a/foo107 [root@andromeda union-testsuite]# stat /mnt/a/foo107 ... Device: 23h/35d Inode: 40346 Links: 1 ... [root@andromeda union-testsuite]# stat -L /proc/$$/fd/5 ... Device: 23h/35d Inode: 40346 Links: 1 ... Note the change in where /proc/$$/fd/5 points to in the ls command. It was pointing to /a/foo107 (which doesn't exist) and now points to /mnt/a/foo107 (which is correct). The inode accessed, however, is the lower layer. The union layer is on device 25h/37d and the upper layer on 24h/36d. Signed-off-by: David Howells Signed-off-by: Al Viro --- fs/open.c | 49 ++++++++++++++++++++++++++----------------------- 1 file changed, 26 insertions(+), 23 deletions(-) (limited to 'fs/open.c') diff --git a/fs/open.c b/fs/open.c index e0250bdcc440..b1c5823b7f11 100644 --- a/fs/open.c +++ b/fs/open.c @@ -678,18 +678,18 @@ int open_check_o_direct(struct file *f) } static int do_dentry_open(struct file *f, + struct inode *inode, int (*open)(struct inode *, struct file *), const struct cred *cred) { static const struct file_operations empty_fops = {}; - struct inode *inode; int error; f->f_mode = OPEN_FMODE(f->f_flags) | FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE; path_get(&f->f_path); - inode = f->f_inode = f->f_path.dentry->d_inode; + f->f_inode = inode; f->f_mapping = inode->i_mapping; if (unlikely(f->f_flags & O_PATH)) { @@ -793,7 +793,8 @@ int finish_open(struct file *file, struct dentry *dentry, BUG_ON(*opened & FILE_OPENED); /* once it's opened, it's opened */ file->f_path.dentry = dentry; - error = do_dentry_open(file, open, current_cred()); + error = do_dentry_open(file, d_backing_inode(dentry), open, + current_cred()); if (!error) *opened |= FILE_OPENED; @@ -822,6 +823,28 @@ int finish_no_open(struct file *file, struct dentry *dentry) } EXPORT_SYMBOL(finish_no_open); +/** + * vfs_open - open the file at the given path + * @path: path to open + * @file: newly allocated file with f_flag initialized + * @cred: credentials to use + */ +int vfs_open(const struct path *path, struct file *file, + const struct cred *cred) +{ + struct dentry *dentry = path->dentry; + struct inode *inode = dentry->d_inode; + + file->f_path = *path; + if (dentry->d_flags & DCACHE_OP_SELECT_INODE) { + inode = dentry->d_op->d_select_inode(dentry, file->f_flags); + if (IS_ERR(inode)) + return PTR_ERR(inode); + } + + return do_dentry_open(file, inode, NULL, cred); +} + struct file *dentry_open(const struct path *path, int flags, const struct cred *cred) { @@ -853,26 +876,6 @@ struct file *dentry_open(const struct path *path, int flags, } EXPORT_SYMBOL(dentry_open); -/** - * vfs_open - open the file at the given path - * @path: path to open - * @filp: newly allocated file with f_flag initialized - * @cred: credentials to use - */ -int vfs_open(const struct path *path, struct file *filp, - const struct cred *cred) -{ - struct inode *inode = path->dentry->d_inode; - - if (inode->i_op->dentry_open) - return inode->i_op->dentry_open(path->dentry, filp, cred); - else { - filp->f_path = *path; - return do_dentry_open(filp, NULL, cred); - } -} -EXPORT_SYMBOL(vfs_open); - static inline int build_open_flags(int flags, umode_t mode, struct open_flags *op) { int lookup_flags = 0; -- cgit v1.2.3-59-g8ed1b