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netfilter: conntrack: free extension area immediately

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Instead of waiting for rcu grace period just free it directly.

This is safe because conntrack lookup doesn't consider extensions.

Other accesses happen while ct->ext can't be free'd, either because
a ct refcount was taken or because the conntrack hash bucket lock or
the dying list spinlock have been taken.

This allows to remove __krealloc in a followup patch, netfilter was the
only user.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal 2019-10-15 15:19:15 +02:00 committed by Pablo Neira Ayuso
parent 49ca022bcc
commit 2ad9d7747c
3 changed files with 10 additions and 23 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

10
include/net/netfilter/nf_conntrack_extend.h
View file

@ -43,7 +43,6 @@ enum nf_ct_ext_id {
/* Extensions: optional stuff which isn't permanently in struct. */ /* Extensions: optional stuff which isn't permanently in struct. */
struct nf_ct_ext { struct nf_ct_ext {
struct rcu_head rcu;
u8 offset[NF_CT_EXT_NUM]; u8 offset[NF_CT_EXT_NUM];
u8 len; u8 len;
char data[0]; char data[0];
@ -72,15 +71,6 @@ static inline void *__nf_ct_ext_find(const struct nf_conn *ct, u8 id)
/* Destroy all relationships */ /* Destroy all relationships */
void nf_ct_ext_destroy(struct nf_conn *ct); void nf_ct_ext_destroy(struct nf_conn *ct);
/* Free operation. If you want to free a object referred from private area,
* please implement __nf_ct_ext_free() and call it.
*/
static inline void nf_ct_ext_free(struct nf_conn *ct)
{
if (ct->ext)
kfree_rcu(ct->ext, rcu);
}
/* Add this type, returns pointer to data or NULL. */ /* Add this type, returns pointer to data or NULL. */
void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp); void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp);

2
net/netfilter/nf_conntrack_core.c
View file

@ -573,7 +573,6 @@ EXPORT_SYMBOL_GPL(nf_ct_tmpl_alloc);
void nf_ct_tmpl_free(struct nf_conn *tmpl) void nf_ct_tmpl_free(struct nf_conn *tmpl)
{ {
nf_ct_ext_destroy(tmpl); nf_ct_ext_destroy(tmpl);
nf_ct_ext_free(tmpl);
if (ARCH_KMALLOC_MINALIGN <= NFCT_INFOMASK) if (ARCH_KMALLOC_MINALIGN <= NFCT_INFOMASK)
kfree((char *)tmpl - tmpl->proto.tmpl_padto); kfree((char *)tmpl - tmpl->proto.tmpl_padto);
@ -1417,7 +1416,6 @@ void nf_conntrack_free(struct nf_conn *ct)
WARN_ON(atomic_read(&ct->ct_general.use) != 0); WARN_ON(atomic_read(&ct->ct_general.use) != 0);
nf_ct_ext_destroy(ct); nf_ct_ext_destroy(ct);
nf_ct_ext_free(ct);
kmem_cache_free(nf_conntrack_cachep, ct); kmem_cache_free(nf_conntrack_cachep, ct);
smp_mb__before_atomic(); smp_mb__before_atomic();
atomic_dec(&net->ct.count); atomic_dec(&net->ct.count);

21
net/netfilter/nf_conntrack_extend.c
View file

@ -34,21 +34,24 @@ void nf_ct_ext_destroy(struct nf_conn *ct)
t->destroy(ct); t->destroy(ct);
rcu_read_unlock(); rcu_read_unlock();
} }
kfree(ct->ext);
} }
EXPORT_SYMBOL(nf_ct_ext_destroy); EXPORT_SYMBOL(nf_ct_ext_destroy);
void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp) void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
{ {
unsigned int newlen, newoff, oldlen, alloc; unsigned int newlen, newoff, oldlen, alloc;
struct nf_ct_ext *old, *new;
struct nf_ct_ext_type *t; struct nf_ct_ext_type *t;
struct nf_ct_ext *new;
/* Conntrack must not be confirmed to avoid races on reallocation. */ /* Conntrack must not be confirmed to avoid races on reallocation. */
WARN_ON(nf_ct_is_confirmed(ct)); WARN_ON(nf_ct_is_confirmed(ct));
old = ct->ext;
if (old) { if (ct->ext) {
const struct nf_ct_ext *old = ct->ext;
if (__nf_ct_ext_exist(old, id)) if (__nf_ct_ext_exist(old, id))
return NULL; return NULL;
oldlen = old->len; oldlen = old->len;
@ -68,22 +71,18 @@ void *nf_ct_ext_add(struct nf_conn *ct, enum nf_ct_ext_id id, gfp_t gfp)
rcu_read_unlock(); rcu_read_unlock();
alloc = max(newlen, NF_CT_EXT_PREALLOC); alloc = max(newlen, NF_CT_EXT_PREALLOC);
kmemleak_not_leak(old); new = krealloc(ct->ext, alloc, gfp);
new = __krealloc(old, alloc, gfp);
if (!new) if (!new)
return NULL; return NULL;
if (!old) { if (!ct->ext)
memset(new->offset, 0, sizeof(new->offset)); memset(new->offset, 0, sizeof(new->offset));
ct->ext = new;
} else if (new != old) {
kfree_rcu(old, rcu);
rcu_assign_pointer(ct->ext, new);
}
new->offset[id] = newoff; new->offset[id] = newoff;
new->len = newlen; new->len = newlen;
memset((void *)new + newoff, 0, newlen - newoff); memset((void *)new + newoff, 0, newlen - newoff);
ct->ext = new;
return (void *)new + newoff; return (void *)new + newoff;
} }
EXPORT_SYMBOL(nf_ct_ext_add); EXPORT_SYMBOL(nf_ct_ext_add);