From 6c4fc209fcf9d27efbaa48368773e4d2bfbd59aa Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sun, 16 Dec 2018 00:49:47 +0100 Subject: [PATCH] bpf: remove useless version check for prog load Existing libraries and tracing frameworks work around this kernel version check by automatically deriving the kernel version from uname(3) or similar such that the user does not need to do it manually; these workarounds also make the version check useless at the same time. Moreover, most other BPF tracing types enabling bpf_probe_read()-like functionality have /not/ adapted this check, and in general these days it is well understood anyway that all the tracing programs are not stable with regards to future kernels as kernel internal data structures are subject to change from release to release. Back at last netconf we discussed [0] and agreed to remove this check from bpf_prog_load() and instead document it here in the uapi header that there is no such guarantee for stable API for these programs. [0] http://vger.kernel.org/netconf2018_files/DanielBorkmann_netconf2018.pdf Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Acked-by: Quentin Monnet Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 10 +++++++++- kernel/bpf/syscall.c | 5 ----- tools/include/uapi/linux/bpf.h | 10 +++++++++- 3 files changed, 18 insertions(+), 7 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index e7d57e89f25f..1d324c2cbca2 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -133,6 +133,14 @@ enum bpf_map_type { BPF_MAP_TYPE_STACK, }; +/* Note that tracing related programs such as + * BPF_PROG_TYPE_{KPROBE,TRACEPOINT,PERF_EVENT,RAW_TRACEPOINT} + * are not subject to a stable API since kernel internal data + * structures can change from release to release and may + * therefore break existing tracing BPF programs. Tracing BPF + * programs correspond to /a/ specific kernel which is to be + * analyzed, and not /a/ specific kernel /and/ all future ones. + */ enum bpf_prog_type { BPF_PROG_TYPE_UNSPEC, BPF_PROG_TYPE_SOCKET_FILTER, @@ -343,7 +351,7 @@ union bpf_attr { __u32 log_level; /* verbosity level of verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied buffer */ - __u32 kern_version; /* checked when prog_type=kprobe */ + __u32 kern_version; /* not used */ __u32 prog_flags; char prog_name[BPF_OBJ_NAME_LEN]; __u32 prog_ifindex; /* ifindex of netdev to prep for */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 6ae062f1cf20..5db31067d85e 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1473,11 +1473,6 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr) if (attr->insn_cnt == 0 || attr->insn_cnt > BPF_MAXINSNS) return -E2BIG; - - if (type == BPF_PROG_TYPE_KPROBE && - attr->kern_version != LINUX_VERSION_CODE) - return -EINVAL; - if (type != BPF_PROG_TYPE_SOCKET_FILTER && type != BPF_PROG_TYPE_CGROUP_SKB && !capable(CAP_SYS_ADMIN)) diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index e7d57e89f25f..1d324c2cbca2 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -133,6 +133,14 @@ enum bpf_map_type { BPF_MAP_TYPE_STACK, }; +/* Note that tracing related programs such as + * BPF_PROG_TYPE_{KPROBE,TRACEPOINT,PERF_EVENT,RAW_TRACEPOINT} + * are not subject to a stable API since kernel internal data + * structures can change from release to release and may + * therefore break existing tracing BPF programs. Tracing BPF + * programs correspond to /a/ specific kernel which is to be + * analyzed, and not /a/ specific kernel /and/ all future ones. + */ enum bpf_prog_type { BPF_PROG_TYPE_UNSPEC, BPF_PROG_TYPE_SOCKET_FILTER, @@ -343,7 +351,7 @@ union bpf_attr { __u32 log_level; /* verbosity level of verifier */ __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied buffer */ - __u32 kern_version; /* checked when prog_type=kprobe */ + __u32 kern_version; /* not used */ __u32 prog_flags; char prog_name[BPF_OBJ_NAME_LEN]; __u32 prog_ifindex; /* ifindex of netdev to prep for */