Revision 88956eabfdea7d01d550535af120d4ef265b1d02 authored by NeilBrown on 12 September 2023, 01:25:00 UTC, committed by Chuck Lever on 12 September 2023, 13:39:35 UTC
If /proc/fs/nfsd/pool_stats is open when the last nfsd thread exits, then when the file is closed a NULL pointer is dereferenced. This is because nfsd_pool_stats_release() assumes that the pointer to the svc_serv cannot become NULL while a reference is held. This used to be the case but a recent patch split nfsd_last_thread() out from nfsd_put(), and clearing the pointer is done in nfsd_last_thread(). This is easily reproduced by running rpc.nfsd 8 ; ( rpc.nfsd 0;true) < /proc/fs/nfsd/pool_stats Fortunately nfsd_pool_stats_release() has easy access to the svc_serv pointer, and so can call svc_put() on it directly. Fixes: 9f28a971ee9f ("nfsd: separate nfsd_last_thread() from nfsd_put()") Signed-off-by: NeilBrown <neilb@suse.de> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
1 parent fdd2630
thread_self.c
// SPDX-License-Identifier: GPL-2.0
#include <linux/cache.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/pid_namespace.h>
#include "internal.h"
/*
* /proc/thread_self:
*/
static const char *proc_thread_self_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
pid_t tgid = task_tgid_nr_ns(current, ns);
pid_t pid = task_pid_nr_ns(current, ns);
char *name;
if (!pid)
return ERR_PTR(-ENOENT);
name = kmalloc(10 + 6 + 10 + 1, dentry ? GFP_KERNEL : GFP_ATOMIC);
if (unlikely(!name))
return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
sprintf(name, "%u/task/%u", tgid, pid);
set_delayed_call(done, kfree_link, name);
return name;
}
static const struct inode_operations proc_thread_self_inode_operations = {
.get_link = proc_thread_self_get_link,
};
static unsigned thread_self_inum __ro_after_init;
int proc_setup_thread_self(struct super_block *s)
{
struct inode *root_inode = d_inode(s->s_root);
struct proc_fs_info *fs_info = proc_sb_info(s);
struct dentry *thread_self;
int ret = -ENOMEM;
inode_lock(root_inode);
thread_self = d_alloc_name(s->s_root, "thread-self");
if (thread_self) {
struct inode *inode = new_inode(s);
if (inode) {
inode->i_ino = thread_self_inum;
inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
inode->i_mode = S_IFLNK | S_IRWXUGO;
inode->i_uid = GLOBAL_ROOT_UID;
inode->i_gid = GLOBAL_ROOT_GID;
inode->i_op = &proc_thread_self_inode_operations;
d_add(thread_self, inode);
ret = 0;
} else {
dput(thread_self);
}
}
inode_unlock(root_inode);
if (ret)
pr_err("proc_fill_super: can't allocate /proc/thread-self\n");
else
fs_info->proc_thread_self = thread_self;
return ret;
}
void __init proc_thread_self_init(void)
{
proc_alloc_inum(&thread_self_inum);
}
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