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77a06c33a2
The eventfs_inode (ei) is protected by SRCU, but the ei->dentry is not. It
is protected by the eventfs_mutex. Anytime the eventfs_mutex is released,
and access to the ei->dentry needs to be done, it should first check if
ei->is_freed is set under the eventfs_mutex. If it is, then the ei->dentry
is invalid and must not be used. The ei->dentry must only be accessed
under the eventfs_mutex and after checking if ei->is_freed is set.
When the ei is being freed, it will (under the eventfs_mutex) set is_freed
and at the same time move the dentry to a free list to be cleared after
the eventfs_mutex is released. This means that any access to the
ei->dentry must check first if ei->is_freed is set, because if it is, then
the dentry is on its way to be freed.
Also add comments to describe this better.
Link: https://lore.kernel.org/all/CA+G9fYt6pY+tMZEOg=SoEywQOe19fGP3uR15SGowkdK+_X85Cg@mail.gmail.com/
Link: https://lore.kernel.org/all/CA+G9fYuDP3hVQ3t7FfrBAjd_WFVSurMgCepTxunSJf=MTe=6aA@mail.gmail.com/
Link: https://lkml.kernel.org/r/20231101172649.477608228@goodmis.org
Cc: Ajay Kaher <akaher@vmware.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 5790b1fb3d ("eventfs: Remove eventfs_file and just use eventfs_inode")
Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reported-by: Beau Belgrave <beaub@linux.microsoft.com>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _TRACEFS_INTERNAL_H
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#define _TRACEFS_INTERNAL_H
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enum {
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TRACEFS_EVENT_INODE = BIT(1),
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TRACEFS_EVENT_TOP_INODE = BIT(2),
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};
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struct tracefs_inode {
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unsigned long flags;
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void *private;
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struct inode vfs_inode;
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};
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/*
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* struct eventfs_inode - hold the properties of the eventfs directories.
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* @list: link list into the parent directory
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* @entries: the array of entries representing the files in the directory
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* @name: the name of the directory to create
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* @children: link list into the child eventfs_inode
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* @dentry: the dentry of the directory
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* @d_parent: pointer to the parent's dentry
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* @d_children: The array of dentries to represent the files when created
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* @data: The private data to pass to the callbacks
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* @is_freed: Flag set if the eventfs is on its way to be freed
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* Note if is_freed is set, then dentry is corrupted.
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* @nr_entries: The number of items in @entries
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*/
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struct eventfs_inode {
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struct list_head list;
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const struct eventfs_entry *entries;
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const char *name;
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struct list_head children;
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struct dentry *dentry; /* Check is_freed to access */
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struct dentry *d_parent;
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struct dentry **d_children;
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void *data;
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/*
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* Union - used for deletion
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* @del_list: list of eventfs_inode to delete
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* @rcu: eventfs_inode to delete in RCU
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*/
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union {
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struct list_head del_list;
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struct rcu_head rcu;
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};
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unsigned int is_freed:1;
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unsigned int nr_entries:31;
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};
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static inline struct tracefs_inode *get_tracefs(const struct inode *inode)
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{
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return container_of(inode, struct tracefs_inode, vfs_inode);
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}
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struct dentry *tracefs_start_creating(const char *name, struct dentry *parent);
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struct dentry *tracefs_end_creating(struct dentry *dentry);
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struct dentry *tracefs_failed_creating(struct dentry *dentry);
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struct inode *tracefs_get_inode(struct super_block *sb);
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struct dentry *eventfs_start_creating(const char *name, struct dentry *parent);
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struct dentry *eventfs_failed_creating(struct dentry *dentry);
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struct dentry *eventfs_end_creating(struct dentry *dentry);
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void eventfs_set_ei_status_free(struct tracefs_inode *ti, struct dentry *dentry);
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#endif /* _TRACEFS_INTERNAL_H */
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