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@xxxxxxxxxxxxxx/ Link: https://lore.kernel.org/linux-trace-kernel/20240523051539.754424703@xxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Fixes: baa23a8d4360d ("tracefs: Reset permissions on remount if permissions are options") Reported-by: Masahiro Yamada <masahiroy@xxxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 5dfb1ccd56ea..129d0f54ba62 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -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 */
