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@iogearbox.net>
Cc: Nicolas Schichan <nschichan@freebox.fr>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 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 @@
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;
}
/**
