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tracefs/eventfs fixes and updates for v6.10:

Browse source 
Bug fixes:
 
 - The eventfs directories need to have unique inode numbers. Make sure that
   they do not get the default file inode number.
 
 - Update the inode uid and gid fields on remount.
   When a remount happens where a uid and/or gid is specified, all the tracefs
   files and directories should get the specified uid and/or gid. But this
   can be sporadic when some uids were assigned already. There's already
   a list of inodes that are allocated. Just update their uid and gid fields
   at the time of remount.
 
 - Update the eventfs_inodes on remount from the top level "events" descriptor.
   There was a bug where not all the eventfs files or directories where
   getting updated on remount. One fix was to clear the SAVED_UID/GID
   flags from the inode list during the iteration of the inodes during
   the remount. But because the eventfs inodes can be freed when the last
   referenced is released, not all the eventfs_inodes were being updated.
   This lead to the ownership selftest to fail if it was run a second
   time (the first time would leave eventfs_inodes with no corresponding
   tracefs_inode).
 
   Instead, for eventfs_inodes, only process the "events" eventfs_inode
   from the list iteration, as it is guaranteed to have a tracefs_inode
   (it's never freed while the "events" directory exists). As it has
   a list of its children, and the children have a list of their children,
   just iterate all the eventfs_inodes from the "events" descriptor and
   it is guaranteed to get all of them.
 
 - Clear the EVENT_INODE flag from the tracefs_drop_inode() callback.
   Currently the EVENTFS_INODE FLAG is cleared in the tracefs_d_iput()
   callback. But this is the wrong location. The iput() callback is
   called when the last reference to the dentry inode is hit. There could
   be a case where two dentry's have the same inode, and the flag will
   be cleared prematurely. The flag needs to be cleared when the last
   reference of the inode is dropped and that happens in the inode's
   drop_inode() callback handler.
 
 Clean ups:
 
 - Consolidate the creation of a tracefs_inode for an eventfs_inode
   A tracefs_inode is created for both files and directories of the
   eventfs system. It is open coded. Instead, consolidate it into a
   single eventfs_get_inode() function call.
 
 - Remove the eventfs getattr and permission callbacks.
   The permissions for the eventfs files and directories are updated
   when the inodes are created, on remount, and when the user sets
   them (via setattr). The inodes hold the current permissions so
   there is no need to have custom getattr or permissions callbacks
   as they will more likely cause them to be incorrect. The inode's
   permissions are updated when they should be updated. Remove the
   getattr and permissions inode callbacks.
 
 - Do not update eventfs_inode attributes on creation of inodes.
   The eventfs_inodes attribute field is used to store the permissions
   of the directories and files for when their corresponding inodes
   are freed and are created again. But when the creation of the inodes
   happen, the eventfs_inode attributes are recalculated. The
   recalculation should only happen when the permissions change for
   a given file or directory. Currently, the attribute changes are
   just being set to their current files so this is not a bug, but
   it's unnecessary and error prone. Stop doing that.
 
 - The events directory inode is created once when the events directory
   is created and deleted when it is deleted. It is now updated on
   remount and when the user changes the permissions. There's no need
   to use the eventfs_inode of the events directory to store the
   events directory permissions. But using it to store the default
   permissions for the files within the directory that have not been
   updated by the user can simplify the code.
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Merge tag 'trace-tracefs-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracefs/eventfs updates from Steven Rostedt:
 "Bug fixes:

   - The eventfs directories need to have unique inode numbers. Make
     sure that they do not get the default file inode number.

   - Update the inode uid and gid fields on remount.

     When a remount happens where a uid and/or gid is specified, all the
     tracefs files and directories should get the specified uid and/or
     gid. But this can be sporadic when some uids were assigned already.
     There's already a list of inodes that are allocated. Just update
     their uid and gid fields at the time of remount.

   - Update the eventfs_inodes on remount from the top level "events"
     descriptor.

     There was a bug where not all the eventfs files or directories
     where getting updated on remount. One fix was to clear the
     SAVED_UID/GID flags from the inode list during the iteration of the
     inodes during the remount. But because the eventfs inodes can be
     freed when the last referenced is released, not all the
     eventfs_inodes were being updated. This lead to the ownership
     selftest to fail if it was run a second time (the first time would
     leave eventfs_inodes with no corresponding tracefs_inode).

     Instead, for eventfs_inodes, only process the "events"
     eventfs_inode from the list iteration, as it is guaranteed to have
     a tracefs_inode (it's never freed while the "events" directory
     exists). As it has a list of its children, and the children have a
     list of their children, just iterate all the eventfs_inodes from
     the "events" descriptor and it is guaranteed to get all of them.

   - Clear the EVENT_INODE flag from the tracefs_drop_inode() callback.

     Currently the EVENTFS_INODE FLAG is cleared in the tracefs_d_iput()
     callback. But this is the wrong location. The iput() callback is
     called when the last reference to the dentry inode is hit. There
     could be a case where two dentry's have the same inode, and the
     flag will be cleared prematurely. The flag needs to be cleared when
     the last reference of the inode is dropped and that happens in the
     inode's drop_inode() callback handler.

  Cleanups:

   - Consolidate the creation of a tracefs_inode for an eventfs_inode

     A tracefs_inode is created for both files and directories of the
     eventfs system. It is open coded. Instead, consolidate it into a
     single eventfs_get_inode() function call.

   - Remove the eventfs getattr and permission callbacks.

     The permissions for the eventfs files and directories are updated
     when the inodes are created, on remount, and when the user sets
     them (via setattr). The inodes hold the current permissions so
     there is no need to have custom getattr or permissions callbacks as
     they will more likely cause them to be incorrect. The inode's
     permissions are updated when they should be updated. Remove the
     getattr and permissions inode callbacks.

   - Do not update eventfs_inode attributes on creation of inodes.

     The eventfs_inodes attribute field is used to store the permissions
     of the directories and files for when their corresponding inodes
     are freed and are created again. But when the creation of the
     inodes happen, the eventfs_inode attributes are recalculated. The
     recalculation should only happen when the permissions change for a
     given file or directory. Currently, the attribute changes are just
     being set to their current files so this is not a bug, but it's
     unnecessary and error prone. Stop doing that.

   - The events directory inode is created once when the events
     directory is created and deleted when it is deleted. It is now
     updated on remount and when the user changes the permissions.
     There's no need to use the eventfs_inode of the events directory to
     store the events directory permissions. But using it to store the
     default permissions for the files within the directory that have
     not been updated by the user can simplify the code"

* tag 'trace-tracefs-v6.10' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  eventfs: Do not use attributes for events directory
  eventfs: Cleanup permissions in creation of inodes
  eventfs: Remove getattr and permission callbacks
  eventfs: Consolidate the eventfs_inode update in eventfs_get_inode()
  tracefs: Clear EVENT_INODE flag in tracefs_drop_inode()
  eventfs: Update all the eventfs_inodes from the events descriptor
  tracefs: Update inode permissions on remount
  eventfs: Keep the directories from having the same inode number as files
This commit is contained in:
Linus Torvalds 2024-05-24 08:27:34 -07:00
parent 6d69b6c12f 2dd00ac1d3
commit 0eb03c7e8e
2 changed files with 128 additions and 167 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

249
fs/tracefs/event_inode.c
View file

@ -37,7 +37,6 @@ static DEFINE_MUTEX(eventfs_mutex);
struct eventfs_root_inode {
struct eventfs_inode ei;
struct inode *parent_inode;
struct dentry *events_dir;
};
@ -50,8 +49,12 @@ static struct eventfs_root_inode *get_root_inode(struct eventfs_inode *ei)
/* Just try to make something consistent and unique */
static int eventfs_dir_ino(struct eventfs_inode *ei)
{
if (!ei->ino)
if (!ei->ino) {
ei->ino = get_next_ino();
/* Must not have the file inode number */
if (ei->ino == EVENTFS_FILE_INODE_INO)
ei->ino = get_next_ino();
}
return ei->ino;
}
@ -207,7 +210,9 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
* determined by the parent directory.
*/
if (dentry->d_inode->i_mode & S_IFDIR) {
update_attr(&ei->attr, iattr);
/* Just use the inode permissions for the events directory */
if (!ei->is_events)
update_attr(&ei->attr, iattr);
} else {
name = dentry->d_name.name;
@ -225,70 +230,9 @@ static int eventfs_set_attr(struct mnt_idmap *idmap, struct dentry *dentry,
return ret;
}
static void update_events_attr(struct eventfs_inode *ei, struct super_block *sb)
{
struct eventfs_root_inode *rei;
struct inode *parent;
rei = get_root_inode(ei);
/* Use the parent inode permissions unless root set its permissions */
parent = rei->parent_inode;
if (rei->ei.attr.mode & EVENTFS_SAVE_UID)
ei->attr.uid = rei->ei.attr.uid;
else
ei->attr.uid = parent->i_uid;
if (rei->ei.attr.mode & EVENTFS_SAVE_GID)
ei->attr.gid = rei->ei.attr.gid;
else
ei->attr.gid = parent->i_gid;
}
static void set_top_events_ownership(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
struct eventfs_inode *ei = ti->private;
/* The top events directory doesn't get automatically updated */
if (!ei || !ei->is_events)
return;
update_events_attr(ei, inode->i_sb);
if (!(ei->attr.mode & EVENTFS_SAVE_UID))
inode->i_uid = ei->attr.uid;
if (!(ei->attr.mode & EVENTFS_SAVE_GID))
inode->i_gid = ei->attr.gid;
}
static int eventfs_get_attr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
{
struct dentry *dentry = path->dentry;
struct inode *inode = d_backing_inode(dentry);
set_top_events_ownership(inode);
generic_fillattr(idmap, request_mask, inode, stat);
return 0;
}
static int eventfs_permission(struct mnt_idmap *idmap,
struct inode *inode, int mask)
{
set_top_events_ownership(inode);
return generic_permission(idmap, inode, mask);
}
static const struct inode_operations eventfs_dir_inode_operations = {
.lookup = eventfs_root_lookup,
.setattr = eventfs_set_attr,
.getattr = eventfs_get_attr,
.permission = eventfs_permission,
};
static const struct inode_operations eventfs_file_inode_operations = {
@ -301,6 +245,45 @@ static const struct file_operations eventfs_file_operations = {
.llseek = generic_file_llseek,
};
static void eventfs_set_attrs(struct eventfs_inode *ei, bool update_uid, kuid_t uid,
bool update_gid, kgid_t gid, int level)
{
struct eventfs_inode *ei_child;
/* Update events/<system>/<event> */
if (WARN_ON_ONCE(level > 3))
return;
if (update_uid) {
ei->attr.mode &= ~EVENTFS_SAVE_UID;
ei->attr.uid = uid;
}
if (update_gid) {
ei->attr.mode &= ~EVENTFS_SAVE_GID;
ei->attr.gid = gid;
}
list_for_each_entry(ei_child, &ei->children, list) {
eventfs_set_attrs(ei_child, update_uid, uid, update_gid, gid, level + 1);
}
if (!ei->entry_attrs)
return;
for (int i = 0; i < ei->nr_entries; i++) {
if (update_uid) {
ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
ei->entry_attrs[i].uid = uid;
}
if (update_gid) {
ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
ei->entry_attrs[i].gid = gid;
}
}
}
/*
* On a remount of tracefs, if UID or GID options are set, then
* the mount point inode permissions should be used.
@ -310,75 +293,61 @@ void eventfs_remount(struct tracefs_inode *ti, bool update_uid, bool update_gid)
{
struct eventfs_inode *ei = ti->private;
if (!ei)
/* Only the events directory does the updates */
if (!ei || !ei->is_events || ei->is_freed)
return;
if (update_uid)
ei->attr.mode &= ~EVENTFS_SAVE_UID;
if (update_gid)
ei->attr.mode &= ~EVENTFS_SAVE_GID;
if (!ei->entry_attrs)
return;
for (int i = 0; i < ei->nr_entries; i++) {
if (update_uid)
ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_UID;
if (update_gid)
ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
}
eventfs_set_attrs(ei, update_uid, ti->vfs_inode.i_uid,
update_gid, ti->vfs_inode.i_gid, 0);
}
/* Return the evenfs_inode of the "events" directory */
static struct eventfs_inode *eventfs_find_events(struct dentry *dentry)
static void update_inode_attr(struct inode *inode, umode_t mode,
struct eventfs_attr *attr, struct eventfs_root_inode *rei)
{
struct eventfs_inode *ei;
do {
// The parent is stable because we do not do renames
dentry = dentry->d_parent;
// ... and directories always have d_fsdata
ei = dentry->d_fsdata;
/*
* If the ei is being freed, the ownership of the children
* doesn't matter.
*/
if (ei->is_freed)
return NULL;
// Walk upwards until you find the events inode
} while (!ei->is_events);
update_events_attr(ei, dentry->d_sb);
return ei;
}
static void update_inode_attr(struct dentry *dentry, struct inode *inode,
struct eventfs_attr *attr, umode_t mode)
{
struct eventfs_inode *events_ei = eventfs_find_events(dentry);
if (!events_ei)
return;
inode->i_mode = mode;
inode->i_uid = events_ei->attr.uid;
inode->i_gid = events_ei->attr.gid;
if (!attr)
return;
if (attr->mode & EVENTFS_SAVE_MODE)
if (attr && attr->mode & EVENTFS_SAVE_MODE)
inode->i_mode = attr->mode & EVENTFS_MODE_MASK;
else
inode->i_mode = mode;
if (attr->mode & EVENTFS_SAVE_UID)
if (attr && attr->mode & EVENTFS_SAVE_UID)
inode->i_uid = attr->uid;
else
inode->i_uid = rei->ei.attr.uid;
if (attr->mode & EVENTFS_SAVE_GID)
if (attr && attr->mode & EVENTFS_SAVE_GID)
inode->i_gid = attr->gid;
else
inode->i_gid = rei->ei.attr.gid;
}
static struct inode *eventfs_get_inode(struct dentry *dentry, struct eventfs_attr *attr,
umode_t mode, struct eventfs_inode *ei)
{
struct eventfs_root_inode *rei;
struct eventfs_inode *pei;
struct tracefs_inode *ti;
struct inode *inode;
inode = tracefs_get_inode(dentry->d_sb);
if (!inode)
return NULL;
ti = get_tracefs(inode);
ti->private = ei;
ti->flags |= TRACEFS_EVENT_INODE;
/* Find the top dentry that holds the "events" directory */
do {
dentry = dentry->d_parent;
/* Directories always have d_fsdata */
pei = dentry->d_fsdata;
} while (!pei->is_events);
rei = get_root_inode(pei);
update_inode_attr(inode, mode, attr, rei);
return inode;
}
/**
@ -401,7 +370,6 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
void *data,
const struct file_operations *fop)
{
struct tracefs_inode *ti;
struct inode *inode;
if (!(mode & S_IFMT))
@ -410,13 +378,11 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
if (WARN_ON_ONCE(!S_ISREG(mode)))
return ERR_PTR(-EIO);
inode = tracefs_get_inode(dentry->d_sb);
/* Only directories have ti->private set to an ei, not files */
inode = eventfs_get_inode(dentry, attr, mode, NULL);
if (unlikely(!inode))
return ERR_PTR(-ENOMEM);
/* If the user updated the directory's attributes, use them */
update_inode_attr(dentry, inode, attr, mode);
inode->i_op = &eventfs_file_inode_operations;
inode->i_fop = fop;
inode->i_private = data;
@ -424,9 +390,6 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
/* All files will have the same inode number */
inode->i_ino = EVENTFS_FILE_INODE_INO;
ti = get_tracefs(inode);
ti->flags |= TRACEFS_EVENT_INODE;
// Files have their parent's ei as their fsdata
dentry->d_fsdata = get_ei(parent_ei);
@ -446,28 +409,19 @@ static struct dentry *lookup_file(struct eventfs_inode *parent_ei,
static struct dentry *lookup_dir_entry(struct dentry *dentry,
struct eventfs_inode *pei, struct eventfs_inode *ei)
{
struct tracefs_inode *ti;
struct inode *inode;
umode_t mode = S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO;
inode = tracefs_get_inode(dentry->d_sb);
inode = eventfs_get_inode(dentry, &ei->attr, mode, ei);
if (unlikely(!inode))
return ERR_PTR(-ENOMEM);
/* If the user updated the directory's attributes, use them */
update_inode_attr(dentry, inode, &ei->attr,
S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO);
inode->i_op = &eventfs_dir_inode_operations;
inode->i_fop = &eventfs_file_operations;
/* All directories will have the same inode number */
inode->i_ino = eventfs_dir_ino(ei);
ti = get_tracefs(inode);
ti->flags |= TRACEFS_EVENT_INODE;
/* Only directories have ti->private set to an ei, not files */
ti->private = ei;
dentry->d_fsdata = get_ei(ei);
d_add(dentry, inode);
@ -828,7 +782,6 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
// Note: we have a ref to the dentry from tracefs_start_creating()
rei = get_root_inode(ei);
rei->events_dir = dentry;
rei->parent_inode = d_inode(dentry->d_sb->s_root);
ei->entries = entries;
ei->nr_entries = size;
@ -838,15 +791,13 @@ struct eventfs_inode *eventfs_create_events_dir(const char *name, struct dentry
uid = d_inode(dentry->d_parent)->i_uid;
gid = d_inode(dentry->d_parent)->i_gid;
/*
* The ei->attr will be used as the default values for the
* files beneath this directory.
*/
ei->attr.uid = uid;
ei->attr.gid = gid;
/*
* When the "events" directory is created, it takes on the
* permissions of its parent. But can be reset on remount.
*/
ei->attr.mode |= EVENTFS_SAVE_UID | EVENTFS_SAVE_GID;
INIT_LIST_HEAD(&ei->children);
INIT_LIST_HEAD(&ei->list);

46
fs/tracefs/inode.c
View file

@ -373,12 +373,21 @@ static int tracefs_apply_options(struct super_block *sb, bool remount)
rcu_read_lock();
list_for_each_entry_rcu(ti, &tracefs_inodes, list) {
if (update_uid)
if (update_uid) {
ti->flags &= ~TRACEFS_UID_PERM_SET;
ti->vfs_inode.i_uid = fsi->uid;
}
if (update_gid)
if (update_gid) {
ti->flags &= ~TRACEFS_GID_PERM_SET;
ti->vfs_inode.i_gid = fsi->gid;
}
/*
* Note, the above ti->vfs_inode updates are
* used in eventfs_remount() so they must come
* before calling it.
*/
if (ti->flags & TRACEFS_EVENT_INODE)
eventfs_remount(ti, update_uid, update_gid);
}
@ -417,10 +426,26 @@ static int tracefs_show_options(struct seq_file *m, struct dentry *root)
return 0;
}
static int tracefs_drop_inode(struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
/*
* This inode is being freed and cannot be used for
* eventfs. Clear the flag so that it doesn't call into
* eventfs during the remount flag updates. The eventfs_inode
* gets freed after an RCU cycle, so the content will still
* be safe if the iteration is going on now.
*/
ti->flags &= ~TRACEFS_EVENT_INODE;
return 1;
}
static const struct super_operations tracefs_super_operations = {
.alloc_inode = tracefs_alloc_inode,
.free_inode = tracefs_free_inode,
.drop_inode = generic_delete_inode,
.drop_inode = tracefs_drop_inode,
.statfs = simple_statfs,
.show_options = tracefs_show_options,
};
@ -446,22 +471,7 @@ static int tracefs_d_revalidate(struct dentry *dentry, unsigned int flags)
return !(ei && ei->is_freed);
}
static void tracefs_d_iput(struct dentry *dentry, struct inode *inode)
{
struct tracefs_inode *ti = get_tracefs(inode);
/*
* This inode is being freed and cannot be used for
* eventfs. Clear the flag so that it doesn't call into
* eventfs during the remount flag updates. The eventfs_inode
* gets freed after an RCU cycle, so the content will still
* be safe if the iteration is going on now.
*/
ti->flags &= ~TRACEFS_EVENT_INODE;
}
static const struct dentry_operations tracefs_dentry_operations = {
.d_iput = tracefs_d_iput,
.d_revalidate = tracefs_d_revalidate,
.d_release = tracefs_d_release,
};