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Date: Wed, 6 May 2015 16:12:30 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: davem@...emloft.net
Cc: ast@...mgrid.com, keescook@...omium.org, nschichan@...ebox.fr,
netdev@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next 4/4] seccomp, filter: add and use bpf_prog_create_from_user from seccomp
Seccomp has always been a special candidate when it comes to preparation
of its filters in seccomp_prepare_filter(). Due to the extra checks and
filter rewrite it partially duplicates code and has BPF internals exposed.
This patch adds a generic API inside the BPF code code that seccomp can use
and thus keep it's filter preparation code minimal and better maintainable.
The other side-effect is that now classic JITs can add seccomp support as
well by only providing a BPF_LDX | BPF_W | BPF_ABS translation.
Tested with seccomp and BPF test suites.
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: Nicolas Schichan <nschichan@...ebox.fr>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Kees Cook <keescook@...omium.org>
---
include/linux/filter.h | 12 +++++-------
kernel/seccomp.c | 42 ++++++++++++-----------------------------
net/core/filter.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 66 insertions(+), 39 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0dcb44b..3c03a60 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -374,19 +374,17 @@ static inline void bpf_prog_unlock_free(struct bpf_prog *fp)
__bpf_prog_free(fp);
}
+typedef int (*bpf_aux_classic_check_t)(struct sock_filter *filter,
+ unsigned int flen);
+
int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog);
+int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
+ bpf_aux_classic_check_t trans);
void bpf_prog_destroy(struct bpf_prog *fp);
int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
int sk_attach_bpf(u32 ufd, struct sock *sk);
int sk_detach_filter(struct sock *sk);
-
-typedef int (*bpf_aux_classic_check_t)(struct sock_filter *filter,
- unsigned int flen);
-
-struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
- bpf_aux_classic_check_t trans);
-
int sk_get_filter(struct sock *sk, struct sock_filter __user *filter,
unsigned int len);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 93d40f7..245df6b 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -346,15 +346,13 @@ static inline void seccomp_sync_threads(void)
*/
static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
- struct seccomp_filter *filter;
- struct bpf_prog *prog;
- unsigned long fsize;
+ struct seccomp_filter *sfilter;
+ int ret;
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
return ERR_PTR(-EINVAL);
BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
- fsize = bpf_classic_proglen(fprog);
/*
* Installing a seccomp filter requires that the task has
@@ -367,37 +365,21 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
CAP_SYS_ADMIN) != 0)
return ERR_PTR(-EACCES);
- prog = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
- if (!prog)
- return ERR_PTR(-ENOMEM);
-
- /* Copy the instructions from fprog. */
- if (copy_from_user(prog->insns, fprog->filter, fsize)) {
- __bpf_prog_free(prog);
- return ERR_PTR(-EFAULT);
- }
-
- prog->len = fprog->len;
-
- /* bpf_prepare_filter() already takes care of freeing
- * memory in case something goes wrong.
- */
- prog = bpf_prepare_filter(prog, seccomp_check_filter);
- if (IS_ERR(prog))
- return ERR_CAST(prog);
-
/* Allocate a new seccomp_filter */
- filter = kzalloc(sizeof(struct seccomp_filter),
- GFP_KERNEL|__GFP_NOWARN);
- if (!filter) {
- bpf_prog_destroy(prog);
+ sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN);
+ if (!sfilter)
return ERR_PTR(-ENOMEM);
+
+ ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
+ seccomp_check_filter);
+ if (ret < 0) {
+ kfree(sfilter);
+ return ERR_PTR(ret);
}
- filter->prog = prog;
- atomic_set(&filter->usage, 1);
+ atomic_set(&sfilter->usage, 1);
- return filter;
+ return sfilter;
}
/**
diff --git a/net/core/filter.c b/net/core/filter.c
index 45c015d..a831f19 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -991,8 +991,8 @@ out_err:
return ERR_PTR(err);
}
-struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
- bpf_aux_classic_check_t trans)
+static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
+ bpf_aux_classic_check_t trans)
{
int err;
@@ -1074,6 +1074,53 @@ int bpf_prog_create(struct bpf_prog **pfp, struct sock_fprog_kern *fprog)
}
EXPORT_SYMBOL_GPL(bpf_prog_create);
+/**
+ * bpf_prog_create_from_user - create an unattached filter from user buffer
+ * @pfp: the unattached filter that is created
+ * @fprog: the filter program
+ * @trans: post-classic verifier transformation handler
+ *
+ * This function effectively does the same as bpf_prog_create(), only
+ * that it builds up its insns buffer from user space provided buffer.
+ * It also allows for passing a bpf_aux_classic_check_t handler.
+ */
+int bpf_prog_create_from_user(struct bpf_prog **pfp, struct sock_fprog *fprog,
+ bpf_aux_classic_check_t trans)
+{
+ unsigned int fsize = bpf_classic_proglen(fprog);
+ struct bpf_prog *fp;
+
+ /* Make sure new filter is there and in the right amounts. */
+ if (fprog->filter == NULL)
+ return -EINVAL;
+
+ fp = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
+ if (!fp)
+ return -ENOMEM;
+
+ if (copy_from_user(fp->insns, fprog->filter, fsize)) {
+ __bpf_prog_free(fp);
+ return -EFAULT;
+ }
+
+ 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;
+
+ /* bpf_prepare_filter() already takes care of freeing
+ * memory in case something goes wrong.
+ */
+ fp = bpf_prepare_filter(fp, trans);
+ if (IS_ERR(fp))
+ return PTR_ERR(fp);
+
+ *pfp = fp;
+ return 0;
+}
+
void bpf_prog_destroy(struct bpf_prog *fp)
{
__bpf_prog_release(fp);
--
1.9.3
--
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