[PATCH net-next v2 2/9] net: filter: keep original BPF program around
From: Daniel Borkmann <hidden>
Date: 2014-03-25 12:11:19
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], networking [sockets], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Martin KaFai Lau, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
In order to open up the possibility to internally transform a BPF program
into an alternative and possibly non-trivial reversible representation, we
need to keep the original BPF program around, so that it can be passed back
to user space w/o the need of a complex decoder.
The reason for that use case resides in commit a8fc92778080 ("sk-filter:
Add ability to get socket filter program (v2)"), that is, the ability
to retrieve the currently attached BPF filter from a given socket used
mainly by the checkpoint-restore project, for example.
Therefore, we add two helpers sk_{store,release}_orig_filter for taking
care of that. In the sk_unattached_filter_create() case, there's no such
possibility/requirement to retrieve a loaded BPF program. Therefore, we
can spare us the work in that case.
This approach will simplify and slightly speed up both, sk_get_filter()
and sock_diag_put_filterinfo() handlers as we won't need to successively
decode filters anymore through sk_decode_filter(). As we still need
sk_decode_filter() later on, we're keeping it around.
Joint work with Alexei Starovoitov.
Signed-off-by: Alexei Starovoitov <redacted>
Signed-off-by: Daniel Borkmann <redacted>
Cc: Pavel Emelyanov <redacted>
---
include/linux/filter.h | 15 +++++++--
net/core/filter.c | 86 ++++++++++++++++++++++++++++++++++++++++----------
net/core/sock_diag.c | 23 ++++++--------
3 files changed, 93 insertions(+), 31 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index e65e230..93a9792 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h@@ -19,14 +19,19 @@ struct compat_sock_fprog { }; #endif +struct sock_fprog_kern { + u16 len; + struct sock_filter *filter; +}; + struct sk_buff; struct sock; -struct sk_filter -{ +struct sk_filter { atomic_t refcnt; u32 jited:1, /* Is our filter JIT'ed? */ len:31; /* Number of filter blocks */ + struct sock_fprog_kern *orig_prog; /* Original BPF program */ struct rcu_head rcu; unsigned int (*bpf_func)(const struct sk_buff *skb, const struct sock_filter *filter);
@@ -42,14 +47,20 @@ static inline unsigned int sk_filter_size(unsigned int proglen) offsetof(struct sk_filter, insns[proglen])); } +#define sk_filter_proglen(fprog) \ + (fprog->len * sizeof(fprog->filter[0])) + extern int sk_filter(struct sock *sk, struct sk_buff *skb); extern unsigned int sk_run_filter(const struct sk_buff *skb, const struct sock_filter *filter); + extern int sk_unattached_filter_create(struct sk_filter **pfp, struct sock_fprog *fprog); extern void sk_unattached_filter_destroy(struct sk_filter *fp); + extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk); extern int sk_detach_filter(struct sock *sk); + extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen); extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len); extern void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to);
diff --git a/net/core/filter.c b/net/core/filter.c
index 2874cc8..f19c078 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -629,6 +629,37 @@ int sk_chk_filter(struct sock_filter *filter, unsigned int flen) } EXPORT_SYMBOL(sk_chk_filter); +static int sk_store_orig_filter(struct sk_filter *fp, + const struct sock_fprog *fprog) +{ + unsigned int fsize = sk_filter_proglen(fprog); + struct sock_fprog_kern *fkprog; + + fp->orig_prog = kmalloc(sizeof(*fkprog), GFP_KERNEL); + if (!fp->orig_prog) + return -ENOMEM; + + fkprog = fp->orig_prog; + fkprog->len = fprog->len; + fkprog->filter = kmemdup(fp->insns, fsize, GFP_KERNEL); + if (!fkprog->filter) { + kfree(fp->orig_prog); + return -ENOMEM; + } + + return 0; +} + +static void sk_release_orig_filter(struct sk_filter *fp) +{ + struct sock_fprog_kern *fprog = fp->orig_prog; + + if (fprog) { + kfree(fprog->filter); + kfree(fprog); + } +} + /** * sk_filter_release_rcu - Release a socket filter by rcu_head * @rcu: rcu_head that contains the sk_filter to free
@@ -637,6 +668,7 @@ void sk_filter_release_rcu(struct rcu_head *rcu) { struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu); + sk_release_orig_filter(fp); bpf_jit_free(fp); } EXPORT_SYMBOL(sk_filter_release_rcu);
@@ -669,8 +701,8 @@ static int __sk_prepare_filter(struct sk_filter *fp) int sk_unattached_filter_create(struct sk_filter **pfp, struct sock_fprog *fprog) { + unsigned int fsize = sk_filter_proglen(fprog); struct sk_filter *fp; - unsigned int fsize = sizeof(struct sock_filter) * fprog->len; int err; /* Make sure new filter is there and in the right amounts. */
@@ -680,10 +712,16 @@ int sk_unattached_filter_create(struct sk_filter **pfp, fp = kmalloc(sk_filter_size(fprog->len), GFP_KERNEL); if (!fp) return -ENOMEM; + memcpy(fp->insns, fprog->filter, fsize); atomic_set(&fp->refcnt, 1); fp->len = fprog->len; + /* Since unattached filters are not copied back to user + * space through sk_get_filter(), we do not need to hold + * a copy here, and can spare us the work. + */ + fp->orig_prog = NULL; err = __sk_prepare_filter(fp); if (err)
@@ -716,7 +754,7 @@ EXPORT_SYMBOL_GPL(sk_unattached_filter_destroy); int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) { struct sk_filter *fp, *old_fp; - unsigned int fsize = sizeof(struct sock_filter) * fprog->len; + unsigned int fsize = sk_filter_proglen(fprog); unsigned int sk_fsize = sk_filter_size(fprog->len); int err;
@@ -730,6 +768,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) fp = sock_kmalloc(sk, sk_fsize, GFP_KERNEL); if (!fp) return -ENOMEM; + if (copy_from_user(fp->insns, fprog->filter, fsize)) { sock_kfree_s(sk, fp, sk_fsize); return -EFAULT;
@@ -738,6 +777,12 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) atomic_set(&fp->refcnt, 1); fp->len = fprog->len; + err = sk_store_orig_filter(fp, fprog); + if (err) { + sk_filter_uncharge(sk, fp); + return -ENOMEM; + } + err = __sk_prepare_filter(fp); if (err) { sk_filter_uncharge(sk, fp);
@@ -750,6 +795,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) if (old_fp) sk_filter_uncharge(sk, old_fp); + return 0; } EXPORT_SYMBOL_GPL(sk_attach_filter);
@@ -769,6 +815,7 @@ int sk_detach_filter(struct sock *sk) sk_filter_uncharge(sk, filter); ret = 0; } + return ret; } EXPORT_SYMBOL_GPL(sk_detach_filter);
@@ -851,34 +898,41 @@ void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to) to->k = filt->k; } -int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf, unsigned int len) +int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf, + unsigned int len) { + struct sock_fprog_kern *fprog; struct sk_filter *filter; - int i, ret; + int ret = 0; lock_sock(sk); filter = rcu_dereference_protected(sk->sk_filter, - sock_owned_by_user(sk)); - ret = 0; + sock_owned_by_user(sk)); if (!filter) goto out; - ret = filter->len; + + /* We're copying the filter that has been originally attached, + * so no conversion/decode needed anymore. + */ + fprog = filter->orig_prog; + + ret = fprog->len; if (!len) + /* User space only enquires number of filter blocks. */ goto out; + ret = -EINVAL; - if (len < filter->len) + if (len < fprog->len) goto out; ret = -EFAULT; - for (i = 0; i < filter->len; i++) { - struct sock_filter fb; - - sk_decode_filter(&filter->insns[i], &fb); - if (copy_to_user(&ubuf[i], &fb, sizeof(fb))) - goto out; - } + if (copy_to_user(ubuf, fprog->filter, sk_filter_proglen(fprog))) + goto out; - ret = filter->len; + /* Instead of bytes, the API requests to return the number + * of filter blocks. + */ + ret = fprog->len; out: release_sock(sk); return ret;
diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index a0e9cf6..d7af188 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c@@ -52,9 +52,10 @@ EXPORT_SYMBOL_GPL(sock_diag_put_meminfo); int sock_diag_put_filterinfo(struct user_namespace *user_ns, struct sock *sk, struct sk_buff *skb, int attrtype) { - struct nlattr *attr; + struct sock_fprog_kern *fprog; struct sk_filter *filter; - unsigned int len; + struct nlattr *attr; + unsigned int flen; int err = 0; if (!ns_capable(user_ns, CAP_NET_ADMIN)) {
@@ -63,24 +64,20 @@ int sock_diag_put_filterinfo(struct user_namespace *user_ns, struct sock *sk, } rcu_read_lock(); - filter = rcu_dereference(sk->sk_filter); - len = filter ? filter->len * sizeof(struct sock_filter) : 0; + if (!filter) + goto out; - attr = nla_reserve(skb, attrtype, len); + fprog = filter->orig_prog; + flen = sk_filter_proglen(fprog); + + attr = nla_reserve(skb, attrtype, flen); if (attr == NULL) { err = -EMSGSIZE; goto out; } - if (filter) { - struct sock_filter *fb = (struct sock_filter *)nla_data(attr); - int i; - - for (i = 0; i < filter->len; i++, fb++) - sk_decode_filter(&filter->insns[i], fb); - } - + memcpy(nla_data(attr), fprog->filter, flen); out: rcu_read_unlock(); return err;
--
1.7.11.7