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debugfs: purge obsolete SRCU based removal protection

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Purge the SRCU based file removal race protection in favour of the new,
refcount based debugfs_file_get()/debugfs_file_put() API.

Fixes: 49d200deaa ("debugfs: prevent access to removed files' private data")
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Nicolai Stange 2017-10-31 00:15:52 +01:00 committed by Greg Kroah-Hartman
parent 7cda7b8f97
commit c9afbec270
4 changed files with 0 additions and 75 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

48
fs/debugfs/file.c
View file

@ -22,7 +22,6 @@
#include <linux/slab.h>
#include <linux/atomic.h>
#include <linux/device.h>
#include <linux/srcu.h>
#include <asm/poll.h>
#include "internal.h"
@ -48,53 +47,6 @@ const struct file_operations debugfs_noop_file_operations = {
.llseek = noop_llseek,
};
/**
* debugfs_use_file_start - mark the beginning of file data access
* @dentry: the dentry object whose data is being accessed.
* @srcu_idx: a pointer to some memory to store a SRCU index in.
*
* Up to a matching call to debugfs_use_file_finish(), any
* successive call into the file removing functions debugfs_remove()
* and debugfs_remove_recursive() will block. Since associated private
* file data may only get freed after a successful return of any of
* the removal functions, you may safely access it after a successful
* call to debugfs_use_file_start() without worrying about
* lifetime issues.
*
* If -%EIO is returned, the file has already been removed and thus,
* it is not safe to access any of its data. If, on the other hand,
* it is allowed to access the file data, zero is returned.
*
* Regardless of the return code, any call to
* debugfs_use_file_start() must be followed by a matching call
* to debugfs_use_file_finish().
*/
int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx)
__acquires(&debugfs_srcu)
{
*srcu_idx = srcu_read_lock(&debugfs_srcu);
barrier();
if (d_unlinked(dentry))
return -EIO;
return 0;
}
EXPORT_SYMBOL_GPL(debugfs_use_file_start);
/**
* debugfs_use_file_finish - mark the end of file data access
* @srcu_idx: the SRCU index "created" by a former call to
* debugfs_use_file_start().
*
* Allow any ongoing concurrent call into debugfs_remove() or
* debugfs_remove_recursive() blocked by a former call to
* debugfs_use_file_start() to proceed and return to its caller.
*/
void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu)
{
srcu_read_unlock(&debugfs_srcu, srcu_idx);
}
EXPORT_SYMBOL_GPL(debugfs_use_file_finish);
#define F_DENTRY(filp) ((filp)->f_path.dentry)
const struct file_operations *debugfs_real_fops(const struct file *filp)

7
fs/debugfs/inode.c
View file

@ -27,14 +27,11 @@
#include <linux/parser.h>
#include <linux/magic.h>
#include <linux/slab.h>
#include <linux/srcu.h>
#include "internal.h"
#define DEBUGFS_DEFAULT_MODE 0700
DEFINE_SRCU(debugfs_srcu);
static struct vfsmount *debugfs_mount;
static int debugfs_mount_count;
static bool debugfs_registered;
@ -693,8 +690,6 @@ void debugfs_remove(struct dentry *dentry)
inode_unlock(d_inode(parent));
if (!ret)
simple_release_fs(&debugfs_mount, &debugfs_mount_count);
synchronize_srcu(&debugfs_srcu);
}
EXPORT_SYMBOL_GPL(debugfs_remove);
@ -768,8 +763,6 @@ void debugfs_remove_recursive(struct dentry *dentry)
if (!__debugfs_remove(child, parent))
simple_release_fs(&debugfs_mount, &debugfs_mount_count);
inode_unlock(d_inode(parent));
synchronize_srcu(&debugfs_srcu);
}
EXPORT_SYMBOL_GPL(debugfs_remove_recursive);

19
include/linux/debugfs.h
View file

@ -23,7 +23,6 @@
struct device;
struct file_operations;
struct srcu_struct;
struct debugfs_blob_wrapper {
void *data;
@ -43,8 +42,6 @@ struct debugfs_regset32 {
extern struct dentry *arch_debugfs_dir;
extern struct srcu_struct debugfs_srcu;
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
static int __fops ## _open(struct inode *inode, struct file *file) \
{ \
@ -90,11 +87,6 @@ struct dentry *debugfs_create_automount(const char *name,
void debugfs_remove(struct dentry *dentry);
void debugfs_remove_recursive(struct dentry *dentry);
int debugfs_use_file_start(const struct dentry *dentry, int *srcu_idx)
__acquires(&debugfs_srcu);
void debugfs_use_file_finish(int srcu_idx) __releases(&debugfs_srcu);
const struct file_operations *debugfs_real_fops(const struct file *filp);
int debugfs_file_get(struct dentry *dentry);
@ -227,17 +219,6 @@ static inline void debugfs_remove(struct dentry *dentry)
static inline void debugfs_remove_recursive(struct dentry *dentry)
{ }
static inline int debugfs_use_file_start(const struct dentry *dentry,
int *srcu_idx)
__acquires(&debugfs_srcu)
{
return 0;
}
static inline void debugfs_use_file_finish(int srcu_idx)
__releases(&debugfs_srcu)
{ }
static inline int debugfs_file_get(struct dentry *dentry)
{
return 0;

1
lib/Kconfig.debug
View file

@ -280,7 +280,6 @@ config PAGE_OWNER
config DEBUG_FS
bool "Debug Filesystem"
select SRCU
help
debugfs is a virtual file system that kernel developers use to put
debugging files into. Enable this option to be able to read and