Commit b4884f23 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: move "struct proc_dir_entry" into kmem cache 

"struct proc_dir_entry" is variable sized because of 0-length trailing
array for name, however, because of SLAB padding allocations it is
possible to make "struct proc_dir_entry" fixed sized and allocate same
amount of memory.

It buys fine-grained debugging with poisoning and usercopy protection
which is not possible with kmalloc-* caches.

Currently, on 32-bit 91+ byte allocations go into kmalloc-128 and on
64-bit 147+ byte allocations go to kmalloc-192 anyway.

Additional memory is allocated only for 38/46+ byte long names which are
rare or may not even exist in the wild.

Link: http://lkml.kernel.org/r/20180223205504.GA17139@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c4219edf

fs/proc/generic.c

+32 −18
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
 * Copyright (C) 1997 Theodore Ts'o

 */



#include <linux/cache.h>

#include <linux/errno.h>

#include <linux/time.h>

#include <linux/proc_fs.h>
@@ -28,6 +29,17 @@ 


static DEFINE_RWLOCK(proc_subdir_lock);



struct kmem_cache *proc_dir_entry_cache __ro_after_init;



void pde_free(struct proc_dir_entry *pde)

{

	if (S_ISLNK(pde->mode))

		kfree(pde->data);

	if (pde->name != pde->inline_name)

		kfree(pde->name);

	kmem_cache_free(proc_dir_entry_cache, pde);

}



static int proc_match(const char *name, struct proc_dir_entry *de, unsigned int len)

{

	if (len < de->namelen)
@@ -363,10 +375,20 @@ static struct proc_dir_entry *__proc_create(struct proc_dir_entry **parent, 
		return NULL;

	}



	ent = kzalloc(sizeof(struct proc_dir_entry) + qstr.len + 1, GFP_KERNEL);

	ent = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);

	if (!ent)

		goto out;



	if (qstr.len + 1 <= sizeof(ent->inline_name)) {

		ent->name = ent->inline_name;

	} else {

		ent->name = kmalloc(qstr.len + 1, GFP_KERNEL);

		if (!ent->name) {

			pde_free(ent);

			return NULL;

		}

	}



	memcpy(ent->name, fn, qstr.len + 1);

	ent->namelen = qstr.len;

	ent->mode = mode;
@@ -395,12 +417,11 @@ struct proc_dir_entry *proc_symlink(const char *name, 
			strcpy((char*)ent->data,dest);

			ent->proc_iops = &proc_link_inode_operations;

			if (proc_register(parent, ent) < 0) {

				kfree(ent->data);

				kfree(ent);

				pde_free(ent);

				ent = NULL;

			}

		} else {

			kfree(ent);

			pde_free(ent);

			ent = NULL;

		}

	}
@@ -423,7 +444,7 @@ struct proc_dir_entry *proc_mkdir_data(const char *name, umode_t mode, 
		ent->proc_iops = &proc_dir_inode_operations;

		parent->nlink++;

		if (proc_register(parent, ent) < 0) {

			kfree(ent);

			pde_free(ent);

			parent->nlink--;

			ent = NULL;

		}
@@ -458,7 +479,7 @@ struct proc_dir_entry *proc_create_mount_point(const char *name) 
		ent->proc_iops = NULL;

		parent->nlink++;

		if (proc_register(parent, ent) < 0) {

			kfree(ent);

			pde_free(ent);

			parent->nlink--;

			ent = NULL;

		}
@@ -495,7 +516,7 @@ struct proc_dir_entry *proc_create_data(const char *name, umode_t mode, 
		goto out_free;

	return pde;

out_free:

	kfree(pde);

	pde_free(pde);

out:

	return NULL;

}
@@ -522,19 +543,12 @@ void proc_set_user(struct proc_dir_entry *de, kuid_t uid, kgid_t gid) 
}

EXPORT_SYMBOL(proc_set_user);



static void free_proc_entry(struct proc_dir_entry *de)

{

	proc_free_inum(de->low_ino);



	if (S_ISLNK(de->mode))

		kfree(de->data);

	kfree(de);

}



void pde_put(struct proc_dir_entry *pde)

{

	if (atomic_dec_and_test(&pde->count))

		free_proc_entry(pde);

	if (atomic_dec_and_test(&pde->count)) {

		proc_free_inum(pde->low_ino);

		pde_free(pde);

	}

}



/*

fs/proc/inode.c

+4 −0
Original line number Diff line number Diff line
@@ -104,6 +104,10 @@ void __init proc_init_kmemcache(void) 
	pde_opener_cache =

		kmem_cache_create("pde_opener", sizeof(struct pde_opener), 0,

				  SLAB_ACCOUNT|SLAB_PANIC, NULL);

	proc_dir_entry_cache = kmem_cache_create_usercopy(

		"proc_dir_entry", sizeof(struct proc_dir_entry), 0, SLAB_PANIC,

		offsetof(struct proc_dir_entry, inline_name),

		sizeof_field(struct proc_dir_entry, inline_name), NULL);

}



static int proc_show_options(struct seq_file *seq, struct dentry *root)

fs/proc/internal.h

+10 −1
Original line number Diff line number Diff line
@@ -52,11 +52,20 @@ struct proc_dir_entry { 
	struct proc_dir_entry *parent;

	struct rb_root_cached subdir;

	struct rb_node subdir_node;

	char *name;

	umode_t mode;

	u8 namelen;

	char name[];

#ifdef CONFIG_64BIT

#define SIZEOF_PDE_INLINE_NAME	(192-147)

#else

#define SIZEOF_PDE_INLINE_NAME	(128-91)

#endif

	char inline_name[SIZEOF_PDE_INLINE_NAME];

} __randomize_layout;



extern struct kmem_cache *proc_dir_entry_cache;

void pde_free(struct proc_dir_entry *pde);



union proc_op {

	int (*proc_get_link)(struct dentry *, struct path *);

	int (*proc_show)(struct seq_file *m,

fs/proc/proc_net.c

+4 −3
Original line number Diff line number Diff line
@@ -192,7 +192,7 @@ static __net_init int proc_net_ns_init(struct net *net) 
	int err;



	err = -ENOMEM;

	netd = kzalloc(sizeof(*netd) + 4, GFP_KERNEL);

	netd = kmem_cache_zalloc(proc_dir_entry_cache, GFP_KERNEL);

	if (!netd)

		goto out;
@@ -201,6 +201,7 @@ static __net_init int proc_net_ns_init(struct net *net) 
	netd->nlink = 2;

	netd->namelen = 3;

	netd->parent = &proc_root;

	netd->name = netd->inline_name;

	memcpy(netd->name, "net", 4);



	uid = make_kuid(net->user_ns, 0);
@@ -223,7 +224,7 @@ static __net_init int proc_net_ns_init(struct net *net) 
	return 0;



free_net:

	kfree(netd);

	pde_free(netd);

out:

	return err;

}
@@ -231,7 +232,7 @@ out: 
static __net_exit void proc_net_ns_exit(struct net *net)

{

	remove_proc_entry("stat", net->proc_net);

	kfree(net->proc_net);

	pde_free(net->proc_net);

}



static struct pernet_operations __net_initdata proc_net_ns_ops = {

fs/proc/root.c

+2 −1
Original line number Diff line number Diff line
@@ -208,7 +208,8 @@ struct proc_dir_entry proc_root = { 
	.proc_fops	= &proc_root_operations,

	.parent		= &proc_root,

	.subdir		= RB_ROOT_CACHED,

	.name		= "/proc",

	.name		= proc_root.inline_name,

	.inline_name	= "/proc",

};



int pid_ns_prepare_proc(struct pid_namespace *ns)

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