From 0ec26fd0698285b31248e34bf1abb022c00f23d6 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Mon, 5 Sep 2011 18:06:26 +0200 Subject: vfs: automount should ignore LOOKUP_FOLLOW Prior to 2.6.38 automount would not trigger on either stat(2) or lstat(2) on the automount point. After 2.6.38, with the introduction of the ->d_automount() infrastructure, stat(2) and others would start triggering automount while lstat(2), etc. still would not. This is a regression and a userspace ABI change. Problem originally reported here: http://thread.gmane.org/gmane.linux.kernel.autofs/6098 It appears that there was an attempt at fixing various userspace tools to not trigger the automount. But since the stat system call is rather common it is impossible to "fix" all userspace. This patch reverts the original behavior, which is to not trigger on stat(2) and other symlink following syscalls. [ It's not really clear what the right behavior is. Apparently Solaris does the "automount on stat, leave alone on lstat". And some programs can get unhappy when "stat+open+fstat" ends up giving a different result from the fstat than from the initial stat. But the change in 2.6.38 resulted in problems for some people, so we're going back to old behavior. Maybe we can re-visit this discussion at some future date - Linus ] Reported-by: Leonardo Chiquitto Signed-off-by: Miklos Szeredi Acked-by: Ian Kent Cc: David Howells Cc: stable@kernel.org Signed-off-by: Linus Torvalds --- fs/namei.c | 33 +++++++++++++++------------------ 1 file changed, 15 insertions(+), 18 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 2826db35dc25..b52bc685465f 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -727,25 +727,22 @@ static int follow_automount(struct path *path, unsigned flags, if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_PARENT)) return -EISDIR; /* we actually want to stop here */ - /* - * We don't want to mount if someone's just doing a stat and they've - * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and - * appended a '/' to the name. + /* We don't want to mount if someone's just doing a stat - + * unless they're stat'ing a directory and appended a '/' to + * the name. + * + * We do, however, want to mount if someone wants to open or + * create a file of any type under the mountpoint, wants to + * traverse through the mountpoint or wants to open the + * mounted directory. Also, autofs may mark negative dentries + * as being automount points. These will need the attentions + * of the daemon to instantiate them before they can be used. */ - if (!(flags & LOOKUP_FOLLOW)) { - /* We do, however, want to mount if someone wants to open or - * create a file of any type under the mountpoint, wants to - * traverse through the mountpoint or wants to open the mounted - * directory. - * Also, autofs may mark negative dentries as being automount - * points. These will need the attentions of the daemon to - * instantiate them before they can be used. - */ - if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | - LOOKUP_OPEN | LOOKUP_CREATE)) && - path->dentry->d_inode) - return -EISDIR; - } + if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | + LOOKUP_OPEN | LOOKUP_CREATE)) && + path->dentry->d_inode) + return -EISDIR; + current->total_link_count++; if (current->total_link_count >= 40) return -ELOOP; -- cgit v1.2.1 From 1d2ef5901483004d74947bbf78d5146c24038fe7 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Wed, 14 Sep 2011 18:55:41 +0100 Subject: restore pinning the victim dentry in vfs_rmdir()/vfs_rename_dir() We used to get the victim pinned by dentry_unhash() prior to commit 64252c75a219 ("vfs: remove dget() from dentry_unhash()") and ->rmdir() and ->rename() instances relied on that; most of them don't care, but ones that used d_delete() themselves do. As the result, we are getting rmdir() oopses on NFS now. Just grab the reference before locking the victim and drop it explicitly after unlocking, same as vfs_rename_other() does. Signed-off-by: Al Viro Tested-by: Simon Kirby Cc: stable@kernel.org (3.0.x) Signed-off-by: Linus Torvalds --- fs/namei.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index b52bc685465f..f4788365ea22 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -2616,6 +2616,7 @@ int vfs_rmdir(struct inode *dir, struct dentry *dentry) if (!dir->i_op->rmdir) return -EPERM; + dget(dentry); mutex_lock(&dentry->d_inode->i_mutex); error = -EBUSY; @@ -2636,6 +2637,7 @@ int vfs_rmdir(struct inode *dir, struct dentry *dentry) out: mutex_unlock(&dentry->d_inode->i_mutex); + dput(dentry); if (!error) d_delete(dentry); return error; @@ -3025,6 +3027,7 @@ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, if (error) return error; + dget(new_dentry); if (target) mutex_lock(&target->i_mutex); @@ -3045,6 +3048,7 @@ static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry, out: if (target) mutex_unlock(&target->i_mutex); + dput(new_dentry); if (!error) if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) d_move(old_dentry,new_dentry); -- cgit v1.2.1 From d94c177beeb4469cd4f6e83354ab0223353e98ed Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 26 Sep 2011 17:44:55 -0700 Subject: vfs pathname lookup: Add LOOKUP_AUTOMOUNT flag Since we've now turned around and made LOOKUP_FOLLOW *not* force an automount, we want to add the ability to force an automount event on lookup even if we don't happen to have one of the other flags that force it implicitly (LOOKUP_OPEN, LOOKUP_DIRECTORY, LOOKUP_PARENT..) Most cases will never want to use this, since you'd normally want to delay automounting as long as possible, which usually implies LOOKUP_OPEN (when we open a file or directory, we really cannot avoid the automount any more). But Trond argued sufficiently forcefully that at a minimum bind mounting a file and quotactl will want to force the automount lookup. Some other cases (like nfs_follow_remote_path()) could use it too, although LOOKUP_DIRECTORY would work there as well. This commit just adds the flag and logic, no users yet, though. It also doesn't actually touch the LOOKUP_NO_AUTOMOUNT flag that is related, and was made irrelevant by the same change that made us not follow on LOOKUP_FOLLOW. Cc: Trond Myklebust Cc: Ian Kent Cc: Jeff Layton Cc: Miklos Szeredi Cc: David Howells Cc: Al Viro Cc: Greg KH Signed-off-by: Linus Torvalds --- fs/namei.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index f4788365ea22..09606fd83d57 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -739,7 +739,7 @@ static int follow_automount(struct path *path, unsigned flags, * of the daemon to instantiate them before they can be used. */ if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY | - LOOKUP_OPEN | LOOKUP_CREATE)) && + LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) && path->dentry->d_inode) return -EISDIR; -- cgit v1.2.1 From b6c8069d3577481390b3f24a8434ad72a3235594 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 27 Sep 2011 08:12:33 -0700 Subject: vfs: remove LOOKUP_NO_AUTOMOUNT flag That flag no longer makes sense, since we don't look up automount points as eagerly any more. Additionally, it turns out that the NO_AUTOMOUNT handling was buggy to begin with: it would avoid automounting even for cases where we really *needed* to do the automount handling, and could return ENOENT for autofs entries that hadn't been instantiated yet. With our new non-eager automount semantics, one discussion has been about adding a AT_AUTOMOUNT flag to vfs_fstatat (and thus the newfstatat() and fstatat64() system calls), but it's probably not worth it: you can always force at least directory automounting by simply adding the final '/' to the filename, which works for *all* of the stat family system calls, old and new. So AT_NO_AUTOMOUNT (and thus LOOKUP_NO_AUTOMOUNT) really were just a result of our bad default behavior. Acked-by: Ian Kent Acked-by: Trond Myklebust Signed-off-by: Linus Torvalds --- fs/namei.c | 6 ------ 1 file changed, 6 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 09606fd83d57..0b3138de2a3b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -721,12 +721,6 @@ static int follow_automount(struct path *path, unsigned flags, if (!path->dentry->d_op || !path->dentry->d_op->d_automount) return -EREMOTE; - /* We don't want to mount if someone supplied AT_NO_AUTOMOUNT - * and this is the terminal part of the path. - */ - if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_PARENT)) - return -EISDIR; /* we actually want to stop here */ - /* We don't want to mount if someone's just doing a stat - * unless they're stat'ing a directory and appended a '/' to * the name. -- cgit v1.2.1