Commit ac67eb2c authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller

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: default avatarDaniel Borkmann <daniel@iogearbox.net>
Cc: Nicolas Schichan <nschichan@freebox.fr>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 658da937
......@@ -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);
......
......@@ -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;
}
/**
......
......@@ -991,8 +991,8 @@ static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)
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);
......
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