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Date: Wed, 6 May 2015 16:12:28 +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 2/4] seccomp: simplify seccomp_prepare_filter and reuse bpf_prepare_filter
From: Nicolas Schichan <nschichan@...ebox.fr>
Remove the calls to bpf_check_classic(), bpf_convert_filter() and
bpf_migrate_runtime() and let bpf_prepare_filter() take care of that
instead.
seccomp_check_filter() is passed to bpf_prepare_filter() so that it
gets called from there, after bpf_check_classic().
We can now remove exposure of two internal classic BPF functions
previously used by seccomp. The export of bpf_check_classic() symbol,
previously known as sk_chk_filter(), was there since pre git times,
and no in-tree module was using it, therefore remove it.
Joint work with Daniel Borkmann.
Signed-off-by: Nicolas Schichan <nschichan@...ebox.fr>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Kees Cook <keescook@...omium.org>
---
include/linux/filter.h | 4 ---
kernel/seccomp.c | 68 ++++++++++++++++----------------------------------
net/core/filter.c | 8 +++---
3 files changed, 26 insertions(+), 54 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 9199624..0dcb44b 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -363,9 +363,6 @@ int sk_filter(struct sock *sk, struct sk_buff *skb);
void bpf_prog_select_runtime(struct bpf_prog *fp);
void bpf_prog_free(struct bpf_prog *fp);
-int bpf_convert_filter(struct sock_filter *prog, int len,
- struct bpf_insn *new_prog, int *new_len);
-
struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags);
struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
gfp_t gfp_extra_flags);
@@ -387,7 +384,6 @@ int sk_detach_filter(struct sock *sk);
typedef int (*bpf_aux_classic_check_t)(struct sock_filter *filter,
unsigned int flen);
-int bpf_check_classic(const struct sock_filter *filter, unsigned int flen);
struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp,
bpf_aux_classic_check_t trans);
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 4f44028..93d40f7 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -347,15 +347,14 @@ static inline void seccomp_sync_threads(void)
static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
{
struct seccomp_filter *filter;
- unsigned long fp_size;
- struct sock_filter *fp;
- int new_len;
- long ret;
+ struct bpf_prog *prog;
+ unsigned long fsize;
if (fprog->len == 0 || fprog->len > BPF_MAXINSNS)
return ERR_PTR(-EINVAL);
+
BUG_ON(INT_MAX / fprog->len < sizeof(struct sock_filter));
- fp_size = fprog->len * sizeof(struct sock_filter);
+ fsize = bpf_classic_proglen(fprog);
/*
* Installing a seccomp filter requires that the task has
@@ -368,60 +367,37 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
CAP_SYS_ADMIN) != 0)
return ERR_PTR(-EACCES);
- fp = kzalloc(fp_size, GFP_KERNEL|__GFP_NOWARN);
- if (!fp)
+ prog = bpf_prog_alloc(bpf_prog_size(fprog->len), 0);
+ if (!prog)
return ERR_PTR(-ENOMEM);
/* Copy the instructions from fprog. */
- ret = -EFAULT;
- if (copy_from_user(fp, fprog->filter, fp_size))
- goto free_prog;
-
- /* Check and rewrite the fprog via the skb checker */
- ret = bpf_check_classic(fp, fprog->len);
- if (ret)
- goto free_prog;
+ if (copy_from_user(prog->insns, fprog->filter, fsize)) {
+ __bpf_prog_free(prog);
+ return ERR_PTR(-EFAULT);
+ }
- /* Check and rewrite the fprog for seccomp use */
- ret = seccomp_check_filter(fp, fprog->len);
- if (ret)
- goto free_prog;
+ prog->len = fprog->len;
- /* Convert 'sock_filter' insns to 'bpf_insn' insns */
- ret = bpf_convert_filter(fp, fprog->len, NULL, &new_len);
- if (ret)
- goto free_prog;
+ /* 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 */
- ret = -ENOMEM;
filter = kzalloc(sizeof(struct seccomp_filter),
GFP_KERNEL|__GFP_NOWARN);
- if (!filter)
- goto free_prog;
-
- filter->prog = bpf_prog_alloc(bpf_prog_size(new_len), __GFP_NOWARN);
- if (!filter->prog)
- goto free_filter;
-
- ret = bpf_convert_filter(fp, fprog->len, filter->prog->insnsi, &new_len);
- if (ret)
- goto free_filter_prog;
+ if (!filter) {
+ bpf_prog_destroy(prog);
+ return ERR_PTR(-ENOMEM);
+ }
- kfree(fp);
+ filter->prog = prog;
atomic_set(&filter->usage, 1);
- filter->prog->len = new_len;
-
- bpf_prog_select_runtime(filter->prog);
return filter;
-
-free_filter_prog:
- __bpf_prog_free(filter->prog);
-free_filter:
- kfree(filter);
-free_prog:
- kfree(fp);
- return ERR_PTR(ret);
}
/**
diff --git a/net/core/filter.c b/net/core/filter.c
index e670494..f887084 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -355,8 +355,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp,
* for socket filters: ctx == 'struct sk_buff *', for seccomp:
* ctx == 'struct seccomp_data *'.
*/
-int bpf_convert_filter(struct sock_filter *prog, int len,
- struct bpf_insn *new_prog, int *new_len)
+static int bpf_convert_filter(struct sock_filter *prog, int len,
+ struct bpf_insn *new_prog, int *new_len)
{
int new_flen = 0, pass = 0, target, i;
struct bpf_insn *new_insn;
@@ -751,7 +751,8 @@ static bool chk_code_allowed(u16 code_to_probe)
*
* Returns 0 if the rule set is legal or -EINVAL if not.
*/
-int bpf_check_classic(const struct sock_filter *filter, unsigned int flen)
+static int bpf_check_classic(const struct sock_filter *filter,
+ unsigned int flen)
{
bool anc_found;
int pc;
@@ -825,7 +826,6 @@ int bpf_check_classic(const struct sock_filter *filter, unsigned int flen)
return -EINVAL;
}
-EXPORT_SYMBOL(bpf_check_classic);
static int bpf_prog_store_orig_filter(struct bpf_prog *fp,
const struct sock_fprog *fprog)
--
1.9.3
--
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