linux-sg2042/include/linux/debugfs.h

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// SPDX-License-Identifier: GPL-2.0
/*
* debugfs.h - a tiny little debug file system
*
* Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
* Copyright (C) 2004 IBM Inc.
*
* debugfs is for people to use instead of /proc or /sys.
* See Documentation/filesystems/ for more details.
*/
#ifndef _DEBUGFS_H_
#define _DEBUGFS_H_
#include <linux/fs.h>
#include <linux/seq_file.h>
#include <linux/types.h>
debugfs: prevent access to removed files' private data Upon return of debugfs_remove()/debugfs_remove_recursive(), it might still be attempted to access associated private file data through previously opened struct file objects. If that data has been freed by the caller of debugfs_remove*() in the meanwhile, the reading/writing process would either encounter a fault or, if the memory address in question has been reassigned again, unrelated data structures could get overwritten. However, since debugfs files are seldomly removed, usually from module exit handlers only, the impact is very low. Currently, there are ~1000 call sites of debugfs_create_file() spread throughout the whole tree and touching all of those struct file_operations in order to make them file removal aware by means of checking the result of debugfs_use_file_start() from within their methods is unfeasible. Instead, wrap the struct file_operations by a lifetime managing proxy at file open: - In debugfs_create_file(), the original fops handed in has got stashed away in ->d_fsdata already. - In debugfs_create_file(), install a proxy file_operations factory, debugfs_full_proxy_file_operations, at ->i_fop. This proxy factory has got an ->open() method only. It carries out some lifetime checks and if successful, dynamically allocates and sets up a new struct file_operations proxy at ->f_op. Afterwards, it forwards to the ->open() of the original struct file_operations in ->d_fsdata, if any. The dynamically set up proxy at ->f_op has got a lifetime managing wrapper set for each of the methods defined in the original struct file_operations in ->d_fsdata. Its ->release()er frees the proxy again and forwards to the original ->release(), if any. In order not to mislead the VFS layer, it is strictly necessary to leave those fields blank in the proxy that have been NULL in the original struct file_operations also, i.e. aren't supported. This is why there is a need for dynamically allocated proxies. The choice made not to allocate a proxy instance for every dentry at file creation, but for every struct file object instantiated thereof is justified by the expected usage pattern of debugfs, namely that in general very few files get opened more than once at a time. The wrapper methods set in the struct file_operations implement lifetime managing by means of the SRCU protection facilities already in place for debugfs: They set up a SRCU read side critical section and check whether the dentry is still alive by means of debugfs_use_file_start(). If so, they forward the call to the original struct file_operation stored in ->d_fsdata, still under the protection of the SRCU read side critical section. This SRCU read side critical section prevents any pending debugfs_remove() and friends to return to their callers. Since a file's private data must only be freed after the return of debugfs_remove(), the ongoing proxied call is guarded against any file removal race. If, on the other hand, the initial call to debugfs_use_file_start() detects that the dentry is dead, the wrapper simply returns -EIO and does not forward the call. Note that the ->poll() wrapper is special in that its signature does not allow for the return of arbitrary -EXXX values and thus, POLLHUP is returned here. In order not to pollute debugfs with wrapper definitions that aren't ever needed, I chose not to define a wrapper for every struct file_operations method possible. Instead, a wrapper is defined only for the subset of methods which are actually set by any debugfs users. Currently, these are: ->llseek() ->read() ->write() ->unlocked_ioctl() ->poll() The ->release() wrapper is special in that it does not protect the original ->release() in any way from dead files in order not to leak resources. Thus, any ->release() handed to debugfs must implement file lifetime management manually, if needed. For only 33 out of a total of 434 releasers handed in to debugfs, it could not be verified immediately whether they access data structures that might have been freed upon a debugfs_remove() return in the meanwhile. Export debugfs_use_file_start() and debugfs_use_file_finish() in order to allow any ->release() to manually implement file lifetime management. For a set of common cases of struct file_operations implemented by the debugfs_core itself, future patches will incorporate file lifetime management directly within those in order to allow for their unproxied operation. Rename the original, non-proxying "debugfs_create_file()" to "debugfs_create_file_unsafe()" and keep it for future internal use by debugfs itself. Factor out code common to both into the new __debugfs_create_file(). Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2016-03-22 21:11:14 +08:00
#include <linux/compiler.h>
struct device;
struct file_operations;
struct debugfs_blob_wrapper {
void *data;
unsigned long size;
};
struct debugfs_reg32 {
char *name;
unsigned long offset;
};
struct debugfs_regset32 {
const struct debugfs_reg32 *regs;
int nregs;
void __iomem *base;
};
extern struct dentry *arch_debugfs_dir;
#define DEFINE_DEBUGFS_ATTRIBUTE(__fops, __get, __set, __fmt) \
static int __fops ## _open(struct inode *inode, struct file *file) \
{ \
__simple_attr_check_format(__fmt, 0ull); \
return simple_attr_open(inode, file, __get, __set, __fmt); \
} \
static const struct file_operations __fops = { \
.owner = THIS_MODULE, \
.open = __fops ## _open, \
.release = simple_attr_release, \
.read = debugfs_attr_read, \
.write = debugfs_attr_write, \
.llseek = no_llseek, \
}
#if defined(CONFIG_DEBUG_FS)
struct dentry *debugfs_lookup(const char *name, struct dentry *parent);
struct dentry *debugfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
struct dentry *debugfs_create_file_unsafe(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops);
struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops,
loff_t file_size);
struct dentry *debugfs_create_dir(const char *name, struct dentry *parent);
struct dentry *debugfs_create_symlink(const char *name, struct dentry *parent,
const char *dest);
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-02-01 01:06:16 +08:00
typedef struct vfsmount *(*debugfs_automount_t)(struct dentry *, void *);
struct dentry *debugfs_create_automount(const char *name,
struct dentry *parent,
fs: Better permission checking for submounts To support unprivileged users mounting filesystems two permission checks have to be performed: a test to see if the user allowed to create a mount in the mount namespace, and a test to see if the user is allowed to access the specified filesystem. The automount case is special in that mounting the original filesystem grants permission to mount the sub-filesystems, to any user who happens to stumble across the their mountpoint and satisfies the ordinary filesystem permission checks. Attempting to handle the automount case by using override_creds almost works. It preserves the idea that permission to mount the original filesystem is permission to mount the sub-filesystem. Unfortunately using override_creds messes up the filesystems ordinary permission checks. Solve this by being explicit that a mount is a submount by introducing vfs_submount, and using it where appropriate. vfs_submount uses a new mount internal mount flags MS_SUBMOUNT, to let sget and friends know that a mount is a submount so they can take appropriate action. sget and sget_userns are modified to not perform any permission checks on submounts. follow_automount is modified to stop using override_creds as that has proven problemantic. do_mount is modified to always remove the new MS_SUBMOUNT flag so that we know userspace will never by able to specify it. autofs4 is modified to stop using current_real_cred that was put in there to handle the previous version of submount permission checking. cifs is modified to pass the mountpoint all of the way down to vfs_submount. debugfs is modified to pass the mountpoint all of the way down to trace_automount by adding a new parameter. To make this change easier a new typedef debugfs_automount_t is introduced to capture the type of the debugfs automount function. Cc: stable@vger.kernel.org Fixes: 069d5ac9ae0d ("autofs: Fix automounts by using current_real_cred()->uid") Fixes: aeaa4a79ff6a ("fs: Call d_automount with the filesystems creds") Reviewed-by: Trond Myklebust <trond.myklebust@primarydata.com> Reviewed-by: Seth Forshee <seth.forshee@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-02-01 01:06:16 +08:00
debugfs_automount_t f,
void *data);
void debugfs_remove(struct dentry *dentry);
void debugfs_remove_recursive(struct dentry *dentry);
const struct file_operations *debugfs_real_fops(const struct file *filp);
debugfs: implement per-file removal protection Since commit 49d200deaa68 ("debugfs: prevent access to removed files' private data"), accesses to a file's private data are protected from concurrent removal by covering all file_operations with a SRCU read section and sychronizing with those before returning from debugfs_remove() by means of synchronize_srcu(). As pointed out by Johannes Berg, there are debugfs files with forever blocking file_operations. Their corresponding SRCU read side sections would block any debugfs_remove() forever as well, even unrelated ones. This results in a livelock. Because a remover can't cancel any indefinite blocking within foreign files, this is a problem. Resolve this by introducing support for more granular protection on a per-file basis. This is implemented by introducing an 'active_users' refcount_t to the per-file struct debugfs_fsdata state. At file creation time, it is set to one and a debugfs_remove() will drop that initial reference. The new debugfs_file_get() and debugfs_file_put(), intended to be used in place of former debugfs_use_file_start() and debugfs_use_file_finish(), increment and decrement it respectively. Once the count drops to zero, debugfs_file_put() will signal a completion which is possibly being waited for from debugfs_remove(). Thus, as long as there is a debugfs_file_get() not yet matched by a corresponding debugfs_file_put() around, debugfs_remove() will block. Actual users of debugfs_use_file_start() and -finish() will get converted to the new debugfs_file_get() and debugfs_file_put() by followup patches. Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Reported-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-10-31 07:15:48 +08:00
int debugfs_file_get(struct dentry *dentry);
void debugfs_file_put(struct dentry *dentry);
ssize_t debugfs_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos);
ssize_t debugfs_attr_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos);
struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
struct dentry *new_dir, const char *new_name);
struct dentry *debugfs_create_u8(const char *name, umode_t mode,
struct dentry *parent, u8 *value);
struct dentry *debugfs_create_u16(const char *name, umode_t mode,
struct dentry *parent, u16 *value);
struct dentry *debugfs_create_u32(const char *name, umode_t mode,
struct dentry *parent, u32 *value);
struct dentry *debugfs_create_u64(const char *name, umode_t mode,
struct dentry *parent, u64 *value);
struct dentry *debugfs_create_ulong(const char *name, umode_t mode,
struct dentry *parent, unsigned long *value);
struct dentry *debugfs_create_x8(const char *name, umode_t mode,
struct dentry *parent, u8 *value);
struct dentry *debugfs_create_x16(const char *name, umode_t mode,
struct dentry *parent, u16 *value);
struct dentry *debugfs_create_x32(const char *name, umode_t mode,
struct dentry *parent, u32 *value);
struct dentry *debugfs_create_x64(const char *name, umode_t mode,
struct dentry *parent, u64 *value);
struct dentry *debugfs_create_size_t(const char *name, umode_t mode,
struct dentry *parent, size_t *value);
struct dentry *debugfs_create_atomic_t(const char *name, umode_t mode,
struct dentry *parent, atomic_t *value);
struct dentry *debugfs_create_bool(const char *name, umode_t mode,
struct dentry *parent, bool *value);
struct dentry *debugfs_create_blob(const char *name, umode_t mode,
struct dentry *parent,
struct debugfs_blob_wrapper *blob);
struct dentry *debugfs_create_regset32(const char *name, umode_t mode,
struct dentry *parent,
struct debugfs_regset32 *regset);
void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
int nregs, void __iomem *base, char *prefix);
struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent,
u32 *array, u32 elements);
struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
struct dentry *parent,
int (*read_fn)(struct seq_file *s,
void *data));
bool debugfs_initialized(void);
ssize_t debugfs_read_file_bool(struct file *file, char __user *user_buf,
size_t count, loff_t *ppos);
ssize_t debugfs_write_file_bool(struct file *file, const char __user *user_buf,
size_t count, loff_t *ppos);
#else
#include <linux/err.h>
/*
* We do not return NULL from these functions if CONFIG_DEBUG_FS is not enabled
* so users have a chance to detect if there was a real error or not. We don't
* want to duplicate the design decision mistakes of procfs and devfs again.
*/
static inline struct dentry *debugfs_lookup(const char *name,
struct dentry *parent)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_file(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_file_unsafe(const char *name,
umode_t mode, struct dentry *parent,
void *data,
const struct file_operations *fops)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_file_size(const char *name, umode_t mode,
struct dentry *parent, void *data,
const struct file_operations *fops,
loff_t file_size)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_dir(const char *name,
struct dentry *parent)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_symlink(const char *name,
struct dentry *parent,
const char *dest)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_automount(const char *name,
struct dentry *parent,
struct vfsmount *(*f)(void *),
void *data)
{
return ERR_PTR(-ENODEV);
}
static inline void debugfs_remove(struct dentry *dentry)
{ }
static inline void debugfs_remove_recursive(struct dentry *dentry)
{ }
const struct file_operations *debugfs_real_fops(const struct file *filp);
debugfs: implement per-file removal protection Since commit 49d200deaa68 ("debugfs: prevent access to removed files' private data"), accesses to a file's private data are protected from concurrent removal by covering all file_operations with a SRCU read section and sychronizing with those before returning from debugfs_remove() by means of synchronize_srcu(). As pointed out by Johannes Berg, there are debugfs files with forever blocking file_operations. Their corresponding SRCU read side sections would block any debugfs_remove() forever as well, even unrelated ones. This results in a livelock. Because a remover can't cancel any indefinite blocking within foreign files, this is a problem. Resolve this by introducing support for more granular protection on a per-file basis. This is implemented by introducing an 'active_users' refcount_t to the per-file struct debugfs_fsdata state. At file creation time, it is set to one and a debugfs_remove() will drop that initial reference. The new debugfs_file_get() and debugfs_file_put(), intended to be used in place of former debugfs_use_file_start() and debugfs_use_file_finish(), increment and decrement it respectively. Once the count drops to zero, debugfs_file_put() will signal a completion which is possibly being waited for from debugfs_remove(). Thus, as long as there is a debugfs_file_get() not yet matched by a corresponding debugfs_file_put() around, debugfs_remove() will block. Actual users of debugfs_use_file_start() and -finish() will get converted to the new debugfs_file_get() and debugfs_file_put() by followup patches. Fixes: 49d200deaa68 ("debugfs: prevent access to removed files' private data") Reported-by: Johannes Berg <johannes@sipsolutions.net> Signed-off-by: Nicolai Stange <nicstange@gmail.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2017-10-31 07:15:48 +08:00
static inline int debugfs_file_get(struct dentry *dentry)
{
return 0;
}
static inline void debugfs_file_put(struct dentry *dentry)
{ }
static inline ssize_t debugfs_attr_read(struct file *file, char __user *buf,
size_t len, loff_t *ppos)
{
return -ENODEV;
}
static inline ssize_t debugfs_attr_write(struct file *file,
const char __user *buf,
size_t len, loff_t *ppos)
{
return -ENODEV;
}
static inline struct dentry *debugfs_rename(struct dentry *old_dir, struct dentry *old_dentry,
struct dentry *new_dir, char *new_name)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_u8(const char *name, umode_t mode,
struct dentry *parent,
u8 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_u16(const char *name, umode_t mode,
struct dentry *parent,
u16 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_u32(const char *name, umode_t mode,
struct dentry *parent,
u32 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_u64(const char *name, umode_t mode,
struct dentry *parent,
u64 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_ulong(const char *name,
umode_t mode,
struct dentry *parent,
unsigned long *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_x8(const char *name, umode_t mode,
struct dentry *parent,
u8 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_x16(const char *name, umode_t mode,
struct dentry *parent,
u16 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_x32(const char *name, umode_t mode,
struct dentry *parent,
u32 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_x64(const char *name, umode_t mode,
struct dentry *parent,
u64 *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_size_t(const char *name, umode_t mode,
struct dentry *parent,
size_t *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_atomic_t(const char *name, umode_t mode,
struct dentry *parent, atomic_t *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_bool(const char *name, umode_t mode,
struct dentry *parent,
bool *value)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_blob(const char *name, umode_t mode,
struct dentry *parent,
struct debugfs_blob_wrapper *blob)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_regset32(const char *name,
umode_t mode, struct dentry *parent,
struct debugfs_regset32 *regset)
{
return ERR_PTR(-ENODEV);
}
static inline void debugfs_print_regs32(struct seq_file *s, const struct debugfs_reg32 *regs,
int nregs, void __iomem *base, char *prefix)
{
}
static inline bool debugfs_initialized(void)
{
return false;
}
static inline struct dentry *debugfs_create_u32_array(const char *name, umode_t mode,
struct dentry *parent,
u32 *array, u32 elements)
{
return ERR_PTR(-ENODEV);
}
static inline struct dentry *debugfs_create_devm_seqfile(struct device *dev,
const char *name,
struct dentry *parent,
int (*read_fn)(struct seq_file *s,
void *data))
{
return ERR_PTR(-ENODEV);
}
static inline ssize_t debugfs_read_file_bool(struct file *file,
char __user *user_buf,
size_t count, loff_t *ppos)
{
return -ENODEV;
}
static inline ssize_t debugfs_write_file_bool(struct file *file,
const char __user *user_buf,
size_t count, loff_t *ppos)
{
return -ENODEV;
}
#endif
#endif