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Commit c9afbec2 authored by Nicolai Stange's avatar Nicolai Stange Committed by Greg Kroah-Hartman
Browse files

debugfs: purge obsolete SRCU based removal protection 



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

Fixes: 49d200de ("debugfs: prevent access to removed files' private data")
Signed-off-by: default avatarNicolai Stange <nicstange@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 7cda7b8f

fs/debugfs/file.c

+0 −48
Original line number Diff line number Diff line
@@ -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)

fs/debugfs/inode.c

+0 −7
Original line number Diff line number Diff line
@@ -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);

include/linux/debugfs.h

+0 −19
Original line number Diff line number Diff line
@@ -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;

lib/Kconfig.debug

+0 −1
Original line number Diff line number Diff line
@@ -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