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eventfs: Update all the eventfs_inodes from the events descriptor

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The change to update the permissions of the eventfs_inode had the
misconception that using the tracefs_inode would find all the
eventfs_inodes that have been updated and reset them on remount.
The problem with this approach is that the eventfs_inodes are freed when
they are no longer used (basically the reason the eventfs system exists).
When they are freed, the updated eventfs_inodes are not reset on a remount
because their tracefs_inodes have been freed.

Instead, since the events directory eventfs_inode always has a
tracefs_inode pointing to it (it is not freed when finished), and the
events directory has a link to all its children, have the
eventfs_remount() function only operate on the events eventfs_inode and
have it descend into its children updating their uid and gids.

Link: https://lore.kernel.org/all/CAK7LNARXgaWw3kH9JgrnH4vK6fr8LDkNKf3wq8NhMWJrVwJyVQ@mail.gmail.com/
Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.754424703@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: baa23a8d43 ("tracefs: Reset permissions on remount if permissions are options")
Reported-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2024-05-23 01:14:28 -04:00
parent 27c0464843
commit 340f0c7067
1 changed files with 43 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

68
fs/tracefs/event_inode.c
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@ -305,6 +305,45 @@ 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.
@ -314,33 +353,12 @@ 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;
ei->attr.uid = ti->vfs_inode.i_uid;
}
if (update_gid) {
ei->attr.mode &= ~EVENTFS_SAVE_GID;
ei->attr.gid = ti->vfs_inode.i_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;
ei->entry_attrs[i].uid = ti->vfs_inode.i_uid;
}
if (update_gid) {
ei->entry_attrs[i].mode &= ~EVENTFS_SAVE_GID;
ei->entry_attrs[i].gid = ti->vfs_inode.i_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 */