original development tree for Linux kernel GTP module; now long in mainline.
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/*
* linux/fs/seq_file.c
*
* helper functions for making synthetic files from sequences of records.
* initial implementation -- AV, Oct 2001.
*/
#include <linux/fs.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/page.h>
/**
* seq_open - initialize sequential file
* @file: file we initialize
* @op: method table describing the sequence
*
* seq_open() sets @file, associating it with a sequence described
* by @op. @op->start() sets the iterator up and returns the first
* element of sequence. @op->stop() shuts it down. @op->next()
* returns the next element of sequence. @op->show() prints element
* into the buffer. In case of error ->start() and ->next() return
* ERR_PTR(error). In the end of sequence they return %NULL. ->show()
* returns 0 in case of success and negative number in case of error.
* Returning SEQ_SKIP means "discard this element and move on".
*/
int seq_open(struct file *file, const struct seq_operations *op)
{
struct seq_file *p = file->private_data;
if (!p) {
p = kmalloc(sizeof(*p), GFP_KERNEL);
if (!p)
return -ENOMEM;
file->private_data = p;
}
memset(p, 0, sizeof(*p));
mutex_init(&p->lock);
p->op = op;
/*
* Wrappers around seq_open(e.g. swaps_open) need to be
* aware of this. If they set f_version themselves, they
* should call seq_open first and then set f_version.
*/
file->f_version = 0;
/*
* seq_files support lseek() and pread(). They do not implement
* write() at all, but we clear FMODE_PWRITE here for historical
* reasons.
*
* If a client of seq_files a) implements file.write() and b) wishes to
* support pwrite() then that client will need to implement its own
* file.open() which calls seq_open() and then sets FMODE_PWRITE.
*/
file->f_mode &= ~FMODE_PWRITE;
return 0;
}
EXPORT_SYMBOL(seq_open);
static int traverse(struct seq_file *m, loff_t offset)
{
loff_t pos = 0, index;
int error = 0;
void *p;
m->version = 0;
index = 0;
m->count = m->from = 0;
if (!offset) {
m->index = index;
return 0;
}
if (!m->buf) {
m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
if (!m->buf)
return -ENOMEM;
}
p = m->op->start(m, &index);
while (p) {
error = PTR_ERR(p);
if (IS_ERR(p))
break;
error = m->op->show(m, p);
if (error < 0)
break;
if (unlikely(error)) {
error = 0;
m->count = 0;
}
if (m->count == m->size)
goto Eoverflow;
if (pos + m->count > offset) {
m->from = offset - pos;
m->count -= m->from;
m->index = index;
break;
}
pos += m->count;
m->count = 0;
if (pos == offset) {
index++;
m->index = index;
break;
}
p = m->op->next(m, p, &index);
}
m->op->stop(m, p);
m->index = index;
return error;
Eoverflow:
m->op->stop(m, p);
kfree(m->buf);
m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
return !m->buf ? -ENOMEM : -EAGAIN;
}
/**
* seq_read - ->read() method for sequential files.
* @file: the file to read from
* @buf: the buffer to read to
* @size: the maximum number of bytes to read
* @ppos: the current position in the file
*
* Ready-made ->f_op->read()
*/
ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
{
struct seq_file *m = file->private_data;
size_t copied = 0;
loff_t pos;
size_t n;
void *p;
int err = 0;
mutex_lock(&m->lock);
/* Don't assume *ppos is where we left it */
if (unlikely(*ppos != m->read_pos)) {
m->read_pos = *ppos;
while ((err = traverse(m, *ppos)) == -EAGAIN)
;
if (err) {
/* With prejudice... */
m->read_pos = 0;
m->version = 0;
m->index = 0;
m->count = 0;
goto Done;
}
}
/*
* seq_file->op->..m_start/m_stop/m_next may do special actions
* or optimisations based on the file->f_version, so we want to
* pass the file->f_version to those methods.
*
* seq_file->version is just copy of f_version, and seq_file
* methods can treat it simply as file version.
* It is copied in first and copied out after all operations.
* It is convenient to have it as part of structure to avoid the
* need of passing another argument to all the seq_file methods.
*/
m->version = file->f_version;
/* grab buffer if we didn't have one */
if (!m->buf) {
m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
if (!m->buf)
goto Enomem;
}
/* if not empty - flush it first */
if (m->count) {
n = min(m->count, size);
err = copy_to_user(buf, m->buf + m->from, n);
if (err)
goto Efault;
m->count -= n;
m->from += n;
size -= n;
buf += n;
copied += n;
if (!m->count)
m->index++;
if (!size)
goto Done;
}
/* we need at least one record in buffer */
pos = m->index;
p = m->op->start(m, &pos);
while (1) {
err = PTR_ERR(p);
if (!p || IS_ERR(p))
break;
err = m->op->show(m, p);
if (err < 0)
break;
if (unlikely(err))
m->count = 0;
if (unlikely(!m->count)) {
p = m->op->next(m, p, &pos);
m->index = pos;
continue;
}
if (m->count < m->size)
goto Fill;
m->op->stop(m, p);
kfree(m->buf);
m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
if (!m->buf)
goto Enomem;
m->count = 0;
m->version = 0;
pos = m->index;
p = m->op->start(m, &pos);
}
m->op->stop(m, p);
m->count = 0;
goto Done;
Fill:
/* they want more? let's try to get some more */
while (m->count < size) {
size_t offs = m->count;
loff_t next = pos;
p = m->op->next(m, p, &next);
if (!p || IS_ERR(p)) {
err = PTR_ERR(p);
break;
}
err = m->op->show(m, p);
if (m->count == m->size || err) {
m->count = offs;
if (likely(err <= 0))
break;
}
pos = next;
}
m->op->stop(m, p);
n = min(m->count, size);
err = copy_to_user(buf, m->buf, n);
if (err)
goto Efault;
copied += n;
m->count -= n;
if (m->count)
m->from = n;
else
pos++;
m->index = pos;
Done:
if (!copied)
copied = err;
else {
*ppos += copied;
m->read_pos += copied;
}
file->f_version = m->version;
mutex_unlock(&m->lock);
return copied;
Enomem:
err = -ENOMEM;
goto Done;
Efault:
err = -EFAULT;
goto Done;
}
EXPORT_SYMBOL(seq_read);
/**
* seq_lseek - ->llseek() method for sequential files.
* @file: the file in question
* @offset: new position
* @origin: 0 for absolute, 1 for relative position
*
* Ready-made ->f_op->llseek()
*/
loff_t seq_lseek(struct file *file, loff_t offset, int origin)
{
struct seq_file *m = file->private_data;
loff_t retval = -EINVAL;
mutex_lock(&m->lock);
m->version = file->f_version;
switch (origin) {
case 1:
offset += file->f_pos;
case 0:
if (offset < 0)
break;
retval = offset;
if (offset != m->read_pos) {
while ((retval=traverse(m, offset)) == -EAGAIN)
;
if (retval) {
/* with extreme prejudice... */
file->f_pos = 0;
m->read_pos = 0;
m->version = 0;
m->index = 0;
m->count = 0;
} else {
m->read_pos = offset;
retval = file->f_pos = offset;
}
}
}
file->f_version = m->version;
mutex_unlock(&m->lock);
return retval;
}
EXPORT_SYMBOL(seq_lseek);
/**
* seq_release - free the structures associated with sequential file.
* @file: file in question
* @inode: file->f_path.dentry->d_inode
*
* Frees the structures associated with sequential file; can be used
* as ->f_op->release() if you don't have private data to destroy.
*/
int seq_release(struct inode *inode, struct file *file)
{
struct seq_file *m = file->private_data;
kfree(m->buf);
kfree(m);
return 0;
}
EXPORT_SYMBOL(seq_release);
/**
* seq_escape - print string into buffer, escaping some characters
* @m: target buffer
* @s: string
* @esc: set of characters that need escaping
*
* Puts string into buffer, replacing each occurrence of character from
* @esc with usual octal escape. Returns 0 in case of success, -1 - in
* case of overflow.
*/
int seq_escape(struct seq_file *m, const char *s, const char *esc)
{
char *end = m->buf + m->size;
char *p;
char c;
for (p = m->buf + m->count; (c = *s) != '\0' && p < end; s++) {
if (!strchr(esc, c)) {
*p++ = c;
continue;
}
if (p + 3 < end) {
*p++ = '\\';
*p++ = '0' + ((c & 0300) >> 6);
*p++ = '0' + ((c & 070) >> 3);
*p++ = '0' + (c & 07);
continue;
}
m->count = m->size;
return -1;
}
m->count = p - m->buf;
return 0;
}
EXPORT_SYMBOL(seq_escape);
int seq_printf(struct seq_file *m, const char *f, ...)
{
va_list args;
int len;
if (m->count < m->size) {
va_start(args, f);
len = vsnprintf(m->buf + m->count, m->size - m->count, f, args);
va_end(args);
if (m->count + len < m->size) {
m->count += len;
return 0;
}
}
m->count = m->size;
return -1;
}
EXPORT_SYMBOL(seq_printf);
/**
* mangle_path - mangle and copy path to buffer beginning
* @s: buffer start
* @p: beginning of path in above buffer
* @esc: set of characters that need escaping
*
* Copy the path from @p to @s, replacing each occurrence of character from
* @esc with usual octal escape.
* Returns pointer past last written character in @s, or NULL in case of
* failure.
*/
char *mangle_path(char *s, const char *p, const char *esc)
{
while (s <= p) {
char c = *p++;
if (!c) {
return s;
} else if (!strchr(esc, c)) {
*s++ = c;
} else if (s + 4 > p) {
break;
} else {
*s++ = '\\';
*s++ = '0' + ((c & 0300) >> 6);
*s++ = '0' + ((c & 070) >> 3);
*s++ = '0' + (c & 07);
}
}
return NULL;
}
EXPORT_SYMBOL(mangle_path);
/**
* seq_path - seq_file interface to print a pathname
* @m: the seq_file handle
* @path: the struct path to print
* @esc: set of characters to escape in the output
*
* return the absolute path of 'path', as represented by the
* dentry / mnt pair in the path parameter.
*/
int seq_path(struct seq_file *m, const struct path *path, const char *esc)
{
char *buf;
size_t size = seq_get_buf(m, &buf);
int res = -1;
if (size) {
char *p = d_path(path, buf, size);
if (!IS_ERR(p)) {
char *end = mangle_path(buf, p, esc);
if (end)
res = end - buf;
}
}
seq_commit(m, res);
return res;
}
EXPORT_SYMBOL(seq_path);
/*
* Same as seq_path, but relative to supplied root.
*/
int seq_path_root(struct seq_file *m, const struct path *path,
const struct path *root, const char *esc)
{
char *buf;
size_t size = seq_get_buf(m, &buf);
int res = -ENAMETOOLONG;
if (size) {
char *p;
p = __d_path(path, root, buf, size);
fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API __d_path() API is asking for trouble and in case of apparmor d_namespace_path() getting just that. The root cause is that when __d_path() misses the root it had been told to look for, it stores the location of the most remote ancestor in *root. Without grabbing references. Sure, at the moment of call it had been pinned down by what we have in *path. And if we raced with umount -l, we could have very well stopped at vfsmount/dentry that got freed as soon as prepend_path() dropped vfsmount_lock. It is safe to compare these pointers with pre-existing (and known to be still alive) vfsmount and dentry, as long as all we are asking is "is it the same address?". Dereferencing is not safe and apparmor ended up stepping into that. d_namespace_path() really wants to examine the place where we stopped, even if it's not connected to our namespace. As the result, it looked at ->d_sb->s_magic of a dentry that might've been already freed by that point. All other callers had been careful enough to avoid that, but it's really a bad interface - it invites that kind of trouble. The fix is fairly straightforward, even though it's bigger than I'd like: * prepend_path() root argument becomes const. * __d_path() is never called with NULL/NULL root. It was a kludge to start with. Instead, we have an explicit function - d_absolute_root(). Same as __d_path(), except that it doesn't get root passed and stops where it stops. apparmor and tomoyo are using it. * __d_path() returns NULL on path outside of root. The main caller is show_mountinfo() and that's precisely what we pass root for - to skip those outside chroot jail. Those who don't want that can (and do) use d_path(). * __d_path() root argument becomes const. Everyone agrees, I hope. * apparmor does *NOT* try to use __d_path() or any of its variants when it sees that path->mnt is an internal vfsmount. In that case it's definitely not mounted anywhere and dentry_path() is exactly what we want there. Handling of sysctl()-triggered weirdness is moved to that place. * if apparmor is asked to do pathname relative to chroot jail and __d_path() tells it we it's not in that jail, the sucker just calls d_absolute_path() instead. That's the other remaining caller of __d_path(), BTW. * seq_path_root() does _NOT_ return -ENAMETOOLONG (it's stupid anyway - the normal seq_file logics will take care of growing the buffer and redoing the call of ->show() just fine). However, if it gets path not reachable from root, it returns SEQ_SKIP. The only caller adjusted (i.e. stopped ignoring the return value as it used to do). Reviewed-by: John Johansen <john.johansen@canonical.com> ACKed-by: John Johansen <john.johansen@canonical.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org
10 years ago
if (!p)
return SEQ_SKIP;
res = PTR_ERR(p);
if (!IS_ERR(p)) {
char *end = mangle_path(buf, p, esc);
if (end)
res = end - buf;
else
res = -ENAMETOOLONG;
}
}
seq_commit(m, res);
fix apparmor dereferencing potentially freed dentry, sanitize __d_path() API __d_path() API is asking for trouble and in case of apparmor d_namespace_path() getting just that. The root cause is that when __d_path() misses the root it had been told to look for, it stores the location of the most remote ancestor in *root. Without grabbing references. Sure, at the moment of call it had been pinned down by what we have in *path. And if we raced with umount -l, we could have very well stopped at vfsmount/dentry that got freed as soon as prepend_path() dropped vfsmount_lock. It is safe to compare these pointers with pre-existing (and known to be still alive) vfsmount and dentry, as long as all we are asking is "is it the same address?". Dereferencing is not safe and apparmor ended up stepping into that. d_namespace_path() really wants to examine the place where we stopped, even if it's not connected to our namespace. As the result, it looked at ->d_sb->s_magic of a dentry that might've been already freed by that point. All other callers had been careful enough to avoid that, but it's really a bad interface - it invites that kind of trouble. The fix is fairly straightforward, even though it's bigger than I'd like: * prepend_path() root argument becomes const. * __d_path() is never called with NULL/NULL root. It was a kludge to start with. Instead, we have an explicit function - d_absolute_root(). Same as __d_path(), except that it doesn't get root passed and stops where it stops. apparmor and tomoyo are using it. * __d_path() returns NULL on path outside of root. The main caller is show_mountinfo() and that's precisely what we pass root for - to skip those outside chroot jail. Those who don't want that can (and do) use d_path(). * __d_path() root argument becomes const. Everyone agrees, I hope. * apparmor does *NOT* try to use __d_path() or any of its variants when it sees that path->mnt is an internal vfsmount. In that case it's definitely not mounted anywhere and dentry_path() is exactly what we want there. Handling of sysctl()-triggered weirdness is moved to that place. * if apparmor is asked to do pathname relative to chroot jail and __d_path() tells it we it's not in that jail, the sucker just calls d_absolute_path() instead. That's the other remaining caller of __d_path(), BTW. * seq_path_root() does _NOT_ return -ENAMETOOLONG (it's stupid anyway - the normal seq_file logics will take care of growing the buffer and redoing the call of ->show() just fine). However, if it gets path not reachable from root, it returns SEQ_SKIP. The only caller adjusted (i.e. stopped ignoring the return value as it used to do). Reviewed-by: John Johansen <john.johansen@canonical.com> ACKed-by: John Johansen <john.johansen@canonical.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org
10 years ago
return res < 0 && res != -ENAMETOOLONG ? res : 0;
}
/*
* returns the path of the 'dentry' from the root of its filesystem.
*/
int seq_dentry(struct seq_file *m, struct dentry *dentry, const char *esc)
{
char *buf;
size_t size = seq_get_buf(m, &buf);
int res = -1;
if (size) {
char *p = dentry_path(dentry, buf, size);
if (!IS_ERR(p)) {
char *end = mangle_path(buf, p, esc);
if (end)
res = end - buf;
}
}
seq_commit(m, res);
return res;
}
int seq_bitmap(struct seq_file *m, const unsigned long *bits,
unsigned int nr_bits)
{
if (m->count < m->size) {
int len = bitmap_scnprintf(m->buf + m->count,
m->size - m->count, bits, nr_bits);
if (m->count + len < m->size) {
m->count += len;
return 0;
}
}
m->count = m->size;
return -1;
}
EXPORT_SYMBOL(seq_bitmap);
int seq_bitmap_list(struct seq_file *m, const unsigned long *bits,
unsigned int nr_bits)
{
if (m->count < m->size) {
int len = bitmap_scnlistprintf(m->buf + m->count,
m->size - m->count, bits, nr_bits);
if (m->count + len < m->size) {
m->count += len;
return 0;
}
}
m->count = m->size;
return -1;
}
EXPORT_SYMBOL(seq_bitmap_list);
static void *single_start(struct seq_file *p, loff_t *pos)
{
return NULL + (*pos == 0);
}
static void *single_next(struct seq_file *p, void *v, loff_t *pos)
{
++*pos;
return NULL;
}
static void single_stop(struct seq_file *p, void *v)
{
}
int single_open(struct file *file, int (*show)(struct seq_file *, void *),
void *data)
{
struct seq_operations *op = kmalloc(sizeof(*op), GFP_KERNEL);
int res = -ENOMEM;
if (op) {
op->start = single_start;
op->next = single_next;
op->stop = single_stop;
op->show = show;
res = seq_open(file, op);
if (!res)
((struct seq_file *)file->private_data)->private = data;
else
kfree(op);
}
return res;
}
EXPORT_SYMBOL(single_open);
int single_release(struct inode *inode, struct file *file)
{
const struct seq_operations *op = ((struct seq_file *)file->private_data)->op;
int res = seq_release(inode, file);
kfree(op);
return res;
}
EXPORT_SYMBOL(single_release);
int seq_release_private(struct inode *inode, struct file *file)
{
struct seq_file *seq = file->private_data;
kfree(seq->private);
seq->private = NULL;
return seq_release(inode, file);
}
EXPORT_SYMBOL(seq_release_private);
void *__seq_open_private(struct file *f, const struct seq_operations *ops,
int psize)
{
int rc;
void *private;
struct seq_file *seq;
private = kzalloc(psize, GFP_KERNEL);
if (private == NULL)
goto out;
rc = seq_open(f, ops);
if (rc < 0)
goto out_free;
seq = f->private_data;
seq->private = private;
return private;
out_free:
kfree(private);
out:
return NULL;
}
EXPORT_SYMBOL(__seq_open_private);
int seq_open_private(struct file *filp, const struct seq_operations *ops,
int psize)
{
return __seq_open_private(filp, ops, psize) ? 0 : -ENOMEM;
}
EXPORT_SYMBOL(seq_open_private);
int seq_putc(struct seq_file *m, char c)
{
if (m->count < m->size) {
m->buf[m->count++] = c;
return 0;
}
return -1;
}
EXPORT_SYMBOL(seq_putc);
int seq_puts(struct seq_file *m, const char *s)
{
int len = strlen(s);
if (m->count + len < m->size) {
memcpy(m->buf + m->count, s, len);
m->count += len;
return 0;
}
m->count = m->size;
return -1;
}
EXPORT_SYMBOL(seq_puts);
/**
* seq_write - write arbitrary data to buffer
* @seq: seq_file identifying the buffer to which data should be written
* @data: data address
* @len: number of bytes
*
* Return 0 on success, non-zero otherwise.
*/
int seq_write(struct seq_file *seq, const void *data, size_t len)
{
if (seq->count + len < seq->size) {
memcpy(seq->buf + seq->count, data, len);
seq->count += len;
return 0;
}
seq->count = seq->size;
return -1;
}
EXPORT_SYMBOL(seq_write);
struct list_head *seq_list_start(struct list_head *head, loff_t pos)
{
struct list_head *lh;
list_for_each(lh, head)
if (pos-- == 0)
return lh;
return NULL;
}
EXPORT_SYMBOL(seq_list_start);
struct list_head *seq_list_start_head(struct list_head *head, loff_t pos)
{
if (!pos)
return head;
return seq_list_start(head, pos - 1);
}
EXPORT_SYMBOL(seq_list_start_head);
struct list_head *seq_list_next(void *v, struct list_head *head, loff_t *ppos)
{
struct list_head *lh;
lh = ((struct list_head *)v)->next;
++*ppos;
return lh == head ? NULL : lh;
}
EXPORT_SYMBOL(seq_list_next);
/**
* seq_hlist_start - start an iteration of a hlist
* @head: the head of the hlist
* @pos: the start position of the sequence
*
* Called at seq_file->op->start().
*/
struct hlist_node *seq_hlist_start(struct hlist_head *head, loff_t pos)
{
struct hlist_node *node;
hlist_for_each(node, head)
if (pos-- == 0)
return node;
return NULL;
}
EXPORT_SYMBOL(seq_hlist_start);
/**
* seq_hlist_start_head - start an iteration of a hlist
* @head: the head of the hlist
* @pos: the start position of the sequence
*
* Called at seq_file->op->start(). Call this function if you want to
* print a header at the top of the output.
*/
struct hlist_node *seq_hlist_start_head(struct hlist_head *head, loff_t pos)
{
if (!pos)
return SEQ_START_TOKEN;
return seq_hlist_start(head, pos - 1);
}
EXPORT_SYMBOL(seq_hlist_start_head);
/**
* seq_hlist_next - move to the next position of the hlist
* @v: the current iterator
* @head: the head of the hlist
* @ppos: the current position
*
* Called at seq_file->op->next().
*/
struct hlist_node *seq_hlist_next(void *v, struct hlist_head *head,
loff_t *ppos)
{
struct hlist_node *node = v;
++*ppos;
if (v == SEQ_START_TOKEN)
return head->first;
else
return node->next;
}
EXPORT_SYMBOL(seq_hlist_next);
/**
* seq_hlist_start_rcu - start an iteration of a hlist protected by RCU
* @head: the head of the hlist
* @pos: the start position of the sequence
*
* Called at seq_file->op->start().
*
* This list-traversal primitive may safely run concurrently with
* the _rcu list-mutation primitives such as hlist_add_head_rcu()
* as long as the traversal is guarded by rcu_read_lock().
*/
struct hlist_node *seq_hlist_start_rcu(struct hlist_head *head,
loff_t pos)
{
struct hlist_node *node;
__hlist_for_each_rcu(node, head)
if (pos-- == 0)
return node;
return NULL;
}
EXPORT_SYMBOL(seq_hlist_start_rcu);
/**
* seq_hlist_start_head_rcu - start an iteration of a hlist protected by RCU
* @head: the head of the hlist
* @pos: the start position of the sequence
*
* Called at seq_file->op->start(). Call this function if you want to
* print a header at the top of the output.
*
* This list-traversal primitive may safely run concurrently with
* the _rcu list-mutation primitives such as hlist_add_head_rcu()
* as long as the traversal is guarded by rcu_read_lock().
*/
struct hlist_node *seq_hlist_start_head_rcu(struct hlist_head *head,
loff_t pos)
{
if (!pos)
return SEQ_START_TOKEN;
return seq_hlist_start_rcu(head, pos - 1);
}
EXPORT_SYMBOL(seq_hlist_start_head_rcu);
/**
* seq_hlist_next_rcu - move to the next position of the hlist protected by RCU
* @v: the current iterator
* @head: the head of the hlist
* @ppos: the current position
*
* Called at seq_file->op->next().
*
* This list-traversal primitive may safely run concurrently with
* the _rcu list-mutation primitives such as hlist_add_head_rcu()
* as long as the traversal is guarded by rcu_read_lock().
*/
struct hlist_node *seq_hlist_next_rcu(void *v,
struct hlist_head *head,
loff_t *ppos)
{
struct hlist_node *node = v;
++*ppos;
if (v == SEQ_START_TOKEN)
return rcu_dereference(head->first);
else
return rcu_dereference(node->next);
}
EXPORT_SYMBOL(seq_hlist_next_rcu);