| Message ID | 20231009124046.74710-4-hengqi.chen@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | seccomp: Make seccomp filter reusable | expand |
On Mon, Oct 09, 2023 at 12:40:45PM +0000, Hengqi Chen wrote: > The SECCOMP_ATTACH_FILTER operation is used to attach > a loaded filter to the current process. The loaded filter > is represented by a fd which is either returned by the > SECCOMP_LOAD_FILTER operation or obtained from bpffs using > bpf syscall. > > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com> > --- > include/uapi/linux/seccomp.h | 1 + > kernel/seccomp.c | 68 +++++++++++++++++++++++++++++++++--- > 2 files changed, 64 insertions(+), 5 deletions(-) > > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h > index ee2c83697810..fbe30262fdfc 100644 > --- a/include/uapi/linux/seccomp.h > +++ b/include/uapi/linux/seccomp.h > @@ -17,6 +17,7 @@ > #define SECCOMP_GET_ACTION_AVAIL 2 > #define SECCOMP_GET_NOTIF_SIZES 3 > #define SECCOMP_LOAD_FILTER 4 > +#define SECCOMP_ATTACH_FILTER 5 > > /* Valid flags for SECCOMP_SET_MODE_FILTER */ > #define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0) > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > index 3ae43db3b642..9f9d8a7a1d6e 100644 > --- a/kernel/seccomp.c > +++ b/kernel/seccomp.c > @@ -523,7 +523,10 @@ static inline pid_t seccomp_can_sync_threads(void) > static inline void seccomp_filter_free(struct seccomp_filter *filter) > { > if (filter) { > - bpf_prog_destroy(filter->prog); > + if (filter->prog->type == BPF_PROG_TYPE_SECCOMP) > + bpf_prog_put(filter->prog); > + else > + bpf_prog_destroy(filter->prog); > kfree(filter); > } > } > @@ -894,7 +897,7 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) > #endif /* SECCOMP_ARCH_NATIVE */ > > /** > - * seccomp_attach_filter: validate and attach filter > + * seccomp_do_attach_filter: validate and attach filter > * @flags: flags to change filter behavior > * @filter: seccomp filter to add to the current process > * > @@ -905,8 +908,8 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) > * seccomp mode or did not have an ancestral seccomp filter > * - in NEW_LISTENER mode: the fd of the new listener > */ > -static long seccomp_attach_filter(unsigned int flags, > - struct seccomp_filter *filter) > +static long seccomp_do_attach_filter(unsigned int flags, > + struct seccomp_filter *filter) > { > unsigned long total_insns; > struct seccomp_filter *walker; > @@ -2001,7 +2004,7 @@ static long seccomp_set_mode_filter(unsigned int flags, > goto out; > } > > - ret = seccomp_attach_filter(flags, prepared); > + ret = seccomp_do_attach_filter(flags, prepared); > if (ret) > goto out; > /* Do not free the successfully attached filter. */ > @@ -2058,6 +2061,51 @@ static long seccomp_load_filter(const char __user *filter) > bpf_prog_put(prog); > return ret; > } > + > +static long seccomp_attach_filter(const char __user *ufd) > +{ > + const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; > + struct seccomp_filter *sfilter; > + struct bpf_prog *prog; > + int flags = 0; > + int fd, ret; > + > + if (copy_from_user(&fd, ufd, sizeof(fd))) > + return -EFAULT; > + > + prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SECCOMP); > + if (IS_ERR(prog)) > + return PTR_ERR(prog); > + > + sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); > + if (!sfilter) { > + bpf_prog_put(prog); > + return -ENOMEM; > + } > + > + sfilter->prog = prog; > + refcount_set(&sfilter->refs, 1); > + refcount_set(&sfilter->users, 1); > + mutex_init(&sfilter->notify_lock); > + init_waitqueue_head(&sfilter->wqh); > + > + spin_lock_irq(¤t->sighand->siglock); > + > + ret = -EINVAL; > + if (!seccomp_may_assign_mode(seccomp_mode)) > + goto out; > + > + ret = seccomp_do_attach_filter(flags, sfilter); > + if (ret) > + goto out; > + > + sfilter = NULL; > + seccomp_assign_mode(current, seccomp_mode, flags); > +out: > + spin_unlock_irq(¤t->sighand->siglock); > + seccomp_filter_free(sfilter); > + return ret; > +} This is duplicating part of seccomp_set_mode_filter() but without handling flags at all. This isn't really workable, since we need things like TSYNC, etc. I think it would be better to adjust SECCOMP_SET_MODE_FILTER to take a new flag that indicates that the user arg is an fd, not a filter. Then the middle of seccomp_set_mode_filter() can choosen between seccomp_prepare_user_filter() and a wrapped call to bpf_prog_get_type() on the fd, etc.
On Wed, Oct 11, 2023 at 8:22 AM Kees Cook <keescook@chromium.org> wrote: > > On Mon, Oct 09, 2023 at 12:40:45PM +0000, Hengqi Chen wrote: > > The SECCOMP_ATTACH_FILTER operation is used to attach > > a loaded filter to the current process. The loaded filter > > is represented by a fd which is either returned by the > > SECCOMP_LOAD_FILTER operation or obtained from bpffs using > > bpf syscall. > > > > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com> > > --- > > include/uapi/linux/seccomp.h | 1 + > > kernel/seccomp.c | 68 +++++++++++++++++++++++++++++++++--- > > 2 files changed, 64 insertions(+), 5 deletions(-) > > > > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h > > index ee2c83697810..fbe30262fdfc 100644 > > --- a/include/uapi/linux/seccomp.h > > +++ b/include/uapi/linux/seccomp.h > > @@ -17,6 +17,7 @@ > > #define SECCOMP_GET_ACTION_AVAIL 2 > > #define SECCOMP_GET_NOTIF_SIZES 3 > > #define SECCOMP_LOAD_FILTER 4 > > +#define SECCOMP_ATTACH_FILTER 5 > > > > /* Valid flags for SECCOMP_SET_MODE_FILTER */ > > #define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0) > > diff --git a/kernel/seccomp.c b/kernel/seccomp.c > > index 3ae43db3b642..9f9d8a7a1d6e 100644 > > --- a/kernel/seccomp.c > > +++ b/kernel/seccomp.c > > @@ -523,7 +523,10 @@ static inline pid_t seccomp_can_sync_threads(void) > > static inline void seccomp_filter_free(struct seccomp_filter *filter) > > { > > if (filter) { > > - bpf_prog_destroy(filter->prog); > > + if (filter->prog->type == BPF_PROG_TYPE_SECCOMP) > > + bpf_prog_put(filter->prog); > > + else > > + bpf_prog_destroy(filter->prog); > > kfree(filter); > > } > > } > > @@ -894,7 +897,7 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) > > #endif /* SECCOMP_ARCH_NATIVE */ > > > > /** > > - * seccomp_attach_filter: validate and attach filter > > + * seccomp_do_attach_filter: validate and attach filter > > * @flags: flags to change filter behavior > > * @filter: seccomp filter to add to the current process > > * > > @@ -905,8 +908,8 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) > > * seccomp mode or did not have an ancestral seccomp filter > > * - in NEW_LISTENER mode: the fd of the new listener > > */ > > -static long seccomp_attach_filter(unsigned int flags, > > - struct seccomp_filter *filter) > > +static long seccomp_do_attach_filter(unsigned int flags, > > + struct seccomp_filter *filter) > > { > > unsigned long total_insns; > > struct seccomp_filter *walker; > > @@ -2001,7 +2004,7 @@ static long seccomp_set_mode_filter(unsigned int flags, > > goto out; > > } > > > > - ret = seccomp_attach_filter(flags, prepared); > > + ret = seccomp_do_attach_filter(flags, prepared); > > if (ret) > > goto out; > > /* Do not free the successfully attached filter. */ > > @@ -2058,6 +2061,51 @@ static long seccomp_load_filter(const char __user *filter) > > bpf_prog_put(prog); > > return ret; > > } > > + > > +static long seccomp_attach_filter(const char __user *ufd) > > +{ > > + const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; > > + struct seccomp_filter *sfilter; > > + struct bpf_prog *prog; > > + int flags = 0; > > + int fd, ret; > > + > > + if (copy_from_user(&fd, ufd, sizeof(fd))) > > + return -EFAULT; > > + > > + prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SECCOMP); > > + if (IS_ERR(prog)) > > + return PTR_ERR(prog); > > + > > + sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); > > + if (!sfilter) { > > + bpf_prog_put(prog); > > + return -ENOMEM; > > + } > > + > > + sfilter->prog = prog; > > + refcount_set(&sfilter->refs, 1); > > + refcount_set(&sfilter->users, 1); > > + mutex_init(&sfilter->notify_lock); > > + init_waitqueue_head(&sfilter->wqh); > > + > > + spin_lock_irq(¤t->sighand->siglock); > > + > > + ret = -EINVAL; > > + if (!seccomp_may_assign_mode(seccomp_mode)) > > + goto out; > > + > > + ret = seccomp_do_attach_filter(flags, sfilter); > > + if (ret) > > + goto out; > > + > > + sfilter = NULL; > > + seccomp_assign_mode(current, seccomp_mode, flags); > > +out: > > + spin_unlock_irq(¤t->sighand->siglock); > > + seccomp_filter_free(sfilter); > > + return ret; > > +} > > This is duplicating part of seccomp_set_mode_filter() but without > handling flags at all. This isn't really workable, since we need things > like TSYNC, etc. I think it would be better to adjust > SECCOMP_SET_MODE_FILTER to take a new flag that indicates that the user > arg is an fd, not a filter. Then the middle of seccomp_set_mode_filter() > can choosen between seccomp_prepare_user_filter() and a wrapped call to > bpf_prog_get_type() on the fd, etc. > Great, that would make things easier. Thanks. > -- > Kees Cook
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index ee2c83697810..fbe30262fdfc 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -17,6 +17,7 @@ #define SECCOMP_GET_ACTION_AVAIL 2 #define SECCOMP_GET_NOTIF_SIZES 3 #define SECCOMP_LOAD_FILTER 4 +#define SECCOMP_ATTACH_FILTER 5 /* Valid flags for SECCOMP_SET_MODE_FILTER */ #define SECCOMP_FILTER_FLAG_TSYNC (1UL << 0) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 3ae43db3b642..9f9d8a7a1d6e 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -523,7 +523,10 @@ static inline pid_t seccomp_can_sync_threads(void) static inline void seccomp_filter_free(struct seccomp_filter *filter) { if (filter) { - bpf_prog_destroy(filter->prog); + if (filter->prog->type == BPF_PROG_TYPE_SECCOMP) + bpf_prog_put(filter->prog); + else + bpf_prog_destroy(filter->prog); kfree(filter); } } @@ -894,7 +897,7 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) #endif /* SECCOMP_ARCH_NATIVE */ /** - * seccomp_attach_filter: validate and attach filter + * seccomp_do_attach_filter: validate and attach filter * @flags: flags to change filter behavior * @filter: seccomp filter to add to the current process * @@ -905,8 +908,8 @@ static void seccomp_cache_prepare(struct seccomp_filter *sfilter) * seccomp mode or did not have an ancestral seccomp filter * - in NEW_LISTENER mode: the fd of the new listener */ -static long seccomp_attach_filter(unsigned int flags, - struct seccomp_filter *filter) +static long seccomp_do_attach_filter(unsigned int flags, + struct seccomp_filter *filter) { unsigned long total_insns; struct seccomp_filter *walker; @@ -2001,7 +2004,7 @@ static long seccomp_set_mode_filter(unsigned int flags, goto out; } - ret = seccomp_attach_filter(flags, prepared); + ret = seccomp_do_attach_filter(flags, prepared); if (ret) goto out; /* Do not free the successfully attached filter. */ @@ -2058,6 +2061,51 @@ static long seccomp_load_filter(const char __user *filter) bpf_prog_put(prog); return ret; } + +static long seccomp_attach_filter(const char __user *ufd) +{ + const unsigned long seccomp_mode = SECCOMP_MODE_FILTER; + struct seccomp_filter *sfilter; + struct bpf_prog *prog; + int flags = 0; + int fd, ret; + + if (copy_from_user(&fd, ufd, sizeof(fd))) + return -EFAULT; + + prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_SECCOMP); + if (IS_ERR(prog)) + return PTR_ERR(prog); + + sfilter = kzalloc(sizeof(*sfilter), GFP_KERNEL | __GFP_NOWARN); + if (!sfilter) { + bpf_prog_put(prog); + return -ENOMEM; + } + + sfilter->prog = prog; + refcount_set(&sfilter->refs, 1); + refcount_set(&sfilter->users, 1); + mutex_init(&sfilter->notify_lock); + init_waitqueue_head(&sfilter->wqh); + + spin_lock_irq(¤t->sighand->siglock); + + ret = -EINVAL; + if (!seccomp_may_assign_mode(seccomp_mode)) + goto out; + + ret = seccomp_do_attach_filter(flags, sfilter); + if (ret) + goto out; + + sfilter = NULL; + seccomp_assign_mode(current, seccomp_mode, flags); +out: + spin_unlock_irq(¤t->sighand->siglock); + seccomp_filter_free(sfilter); + return ret; +} #else static inline long seccomp_set_mode_filter(unsigned int flags, const char __user *filter) @@ -2069,6 +2117,11 @@ static inline long seccomp_load_filter(const char __user *filter) { return -EINVAL; } + +static inline long seccomp_attach_filter(const char __user *ufd) +{ + return -EINVAL; +} #endif static long seccomp_get_action_avail(const char __user *uaction) @@ -2135,6 +2188,11 @@ static long do_seccomp(unsigned int op, unsigned int flags, return -EINVAL; return seccomp_load_filter(uargs); + case SECCOMP_ATTACH_FILTER: + if (flags != 0) + return -EINVAL; + + return seccomp_attach_filter(uargs); default: return -EINVAL; }
The SECCOMP_ATTACH_FILTER operation is used to attach a loaded filter to the current process. The loaded filter is represented by a fd which is either returned by the SECCOMP_LOAD_FILTER operation or obtained from bpffs using bpf syscall. Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com> --- include/uapi/linux/seccomp.h | 1 + kernel/seccomp.c | 68 +++++++++++++++++++++++++++++++++--- 2 files changed, 64 insertions(+), 5 deletions(-)