From: Alexey Dobriyan <adobriyan@xxxxxxxxx> Subject: 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: Alexey Dobriyan <adobriyan@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/proc/generic.c | 50 +++++++++++++++++++++++++++---------------- fs/proc/inode.c | 4 +++ fs/proc/internal.h | 11 ++++++++- fs/proc/proc_net.c | 7 +++--- fs/proc/root.c | 3 +- 5 files changed, 52 insertions(+), 23 deletions(-) diff -puN fs/proc/generic.c~proc-move-struct-proc_dir_entry-into-kmem-cache fs/proc/generic.c --- a/fs/proc/generic.c~proc-move-struct-proc_dir_entry-into-kmem-cache +++ a/fs/proc/generic.c @@ -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_cre 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(cons 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(c 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 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( 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 } 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); + } } /* diff -puN fs/proc/inode.c~proc-move-struct-proc_dir_entry-into-kmem-cache fs/proc/inode.c --- a/fs/proc/inode.c~proc-move-struct-proc_dir_entry-into-kmem-cache +++ a/fs/proc/inode.c @@ -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) diff -puN fs/proc/internal.h~proc-move-struct-proc_dir_entry-into-kmem-cache fs/proc/internal.h --- a/fs/proc/internal.h~proc-move-struct-proc_dir_entry-into-kmem-cache +++ a/fs/proc/internal.h @@ -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, diff -puN fs/proc/proc_net.c~proc-move-struct-proc_dir_entry-into-kmem-cache fs/proc/proc_net.c --- a/fs/proc/proc_net.c~proc-move-struct-proc_dir_entry-into-kmem-cache +++ a/fs/proc/proc_net.c @@ -192,7 +192,7 @@ static __net_init int proc_net_ns_init(s 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(s 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(s 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 = { diff -puN fs/proc/root.c~proc-move-struct-proc_dir_entry-into-kmem-cache fs/proc/root.c --- a/fs/proc/root.c~proc-move-struct-proc_dir_entry-into-kmem-cache +++ a/fs/proc/root.c @@ -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) _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
