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vfs: generate FS_CREATE before FS_OPEN when ->atomic_open used.

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When a file is opened and created with open(..., O_CREAT) we get
both the CREATE and OPEN fsnotify events and would expect them in that
order.   For most filesystems we get them in that order because
open_last_lookups() calls fsnofify_create() and then do_open() (from
path_openat()) calls vfs_open()->do_dentry_open() which calls
fsnotify_open().

However when ->atomic_open is used, the
   do_dentry_open() -> fsnotify_open()
call happens from finish_open() which is called from the ->atomic_open
handler in lookup_open() which is called *before* open_last_lookups()
calls fsnotify_create.  So we get the "open" notification before
"create" - which is backwards.  ltp testcase inotify02 tests this and
reports the inconsistency.

This patch lifts the fsnotify_open() call out of do_dentry_open() and
places it higher up the call stack.  There are three callers of
do_dentry_open().

For vfs_open() and kernel_file_open() the fsnotify_open() is placed
directly in that caller so there should be no behavioural change.

For finish_open() there are two cases:
 - finish_open is used in ->atomic_open handlers.  For these we add a
   call to fsnotify_open() at open_last_lookups() if FMODE_OPENED is
   set - which means do_dentry_open() has been called.
 - finish_open is used in ->tmpfile() handlers.  For these a similar
   call to fsnotify_open() is added to vfs_tmpfile()

With this patch NFSv3 is restored to its previous behaviour (before
->atomic_open support was added) of generating CREATE notifications
before OPEN, and NFSv4 now has that same correct ordering that is has
not had before.  I haven't tested other filesystems.

Fixes: 7c6c5249f0 ("NFS: add atomic_open for NFSv3 to handle O_TRUNC correctly.")
Reported-by: James Clark <james.clark@arm.com>
Closes: https://lore.kernel.org/all/01c3bf2e-eb1f-4b7f-a54f-d2a05dd3d8c8@arm.com
Signed-off-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/171817619547.14261.975798725161704336@noble.neil.brown.name
Fixes: 7b8c9d7bb4 ("fsnotify: move fsnotify_open() hook into do_dentry_open()")
Tested-by: James Clark <james.clark@arm.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240617162303.1596-2-jack@suse.cz
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
NeilBrown 2024-06-17 18:23:01 +02:00 committed by Christian Brauner
parent 702eb71fd6
commit 7d1cf5e624
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 23 additions and 9 deletions
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10
fs/namei.c
View File

@ -3572,8 +3572,12 @@ static const char *open_last_lookups(struct nameidata *nd,
else
inode_lock_shared(dir->d_inode);
dentry = lookup_open(nd, file, op, got_write);
if (!IS_ERR(dentry) && (file->f_mode & FMODE_CREATED))
fsnotify_create(dir->d_inode, dentry);
if (!IS_ERR(dentry)) {
if (file->f_mode & FMODE_CREATED)
fsnotify_create(dir->d_inode, dentry);
if (file->f_mode & FMODE_OPENED)
fsnotify_open(file);
}
if (open_flag & O_CREAT)
inode_unlock(dir->d_inode);
else
@ -3700,6 +3704,8 @@ int vfs_tmpfile(struct mnt_idmap *idmap,
mode = vfs_prepare_mode(idmap, dir, mode, mode, mode);
error = dir->i_op->tmpfile(idmap, dir, file, mode);
dput(child);
if (file->f_mode & FMODE_OPENED)
fsnotify_open(file);
if (error)
return error;
/* Don't check for other permissions, the inode was just created */

22
fs/open.c
View File

@ -1004,11 +1004,6 @@ static int do_dentry_open(struct file *f,
}
}
/*
* Once we return a file with FMODE_OPENED, __fput() will call
* fsnotify_close(), so we need fsnotify_open() here for symmetry.
*/
fsnotify_open(f);
return 0;
cleanup_all:
@ -1085,8 +1080,19 @@ EXPORT_SYMBOL(file_path);
*/
int vfs_open(const struct path *path, struct file *file)
{
int ret;
file->f_path = *path;
return do_dentry_open(file, NULL);
ret = do_dentry_open(file, NULL);
if (!ret) {
/*
* Once we return a file with FMODE_OPENED, __fput() will call
* fsnotify_close(), so we need fsnotify_open() here for
* symmetry.
*/
fsnotify_open(file);
}
return ret;
}
struct file *dentry_open(const struct path *path, int flags,
@ -1177,8 +1183,10 @@ struct file *kernel_file_open(const struct path *path, int flags,
error = do_dentry_open(f, NULL);
if (error) {
fput(f);
f = ERR_PTR(error);
return ERR_PTR(error);
}
fsnotify_open(f);
return f;
}
EXPORT_SYMBOL_GPL(kernel_file_open);