Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Medium] bpf: inaccurate attach_type and prog_type error logging in link_create() --
commit bc490436683f8010bb5c27c3e3a1582ddc24a909 Author: Leon Hwang <[email protected]> bpf: Add syscall common attrs support for link_create This commit adds syscall common attributes support to link_create() in kernel/bpf/syscall.c, initializing and finalizing a bpf_verifier_log instance to report errors for invalid prog_fd, attach_type, and prog_type. Link: https://lore.kernel.org/bpf/[email protected]/ > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 90bc7230afa8a..db870e795d044 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -5862,8 +5862,11 @@ static int bpf_map_do_batch(const union bpf_attr *attr, > } > > #define BPF_LINK_CREATE_LAST_FIELD link_create.uprobe_multi.path_fd > -static int link_create(union bpf_attr *attr, bpfptr_t uattr) > +static int link_create(union bpf_attr *attr, bpfptr_t uattr, struct > bpf_common_attr *attr_common, > + bpfptr_t uattr_common, u32 size_common) > { > + struct bpf_verifier_log *log; > + struct bpf_log_attr attr_log; > struct bpf_prog *prog; > int ret; > > @@ -5873,14 +5876,24 @@ static int link_create(union bpf_attr *attr, bpfptr_t > uattr) > if (attr->link_create.attach_type == BPF_STRUCT_OPS) > return bpf_struct_ops_link_create(attr); > > + log = bpf_log_attr_create_vlog(&attr_log, attr_common, uattr_common, > size_common); > + if (IS_ERR(log)) > + return PTR_ERR(log); > + > prog = bpf_prog_get(attr->link_create.prog_fd); > - if (IS_ERR(prog)) > - return PTR_ERR(prog); > + if (IS_ERR(prog)) { > + bpf_log(log, "Invalid prog_fd.\n"); > + ret = PTR_ERR(prog); > + prog = NULL; > + goto out; > + } > > ret = bpf_prog_attach_check_attach_type(prog, > attr->link_create.attach_type); > - if (ret) > + if (ret) { > + bpf_log(log, "Invalid attach_type.\n"); > goto out; > + } > > switch (prog->type) { > case BPF_PROG_TYPE_CGROUP_SKB: > @@ -5959,12 +5972,20 @@ static int link_create(union bpf_attr *attr, bpfptr_t > uattr) > ret = bpf_uprobe_multi_link_attach(attr, prog); > break; > default: > + bpf_log(log, "Invalid prog type.\n"); > ret = -EINVAL; > } [Severity: Medium] Does calling bpf_prog_attach_check_attach_type() before switch (prog->type) in kernel/bpf/syscall.c:link_create() cause misleading or missing log messages in a few cases? First, for almost all program types that are unsupported by link_create() (such as BPF_PROG_TYPE_SOCKET_FILTER, BPF_PROG_TYPE_SCHED_ACT, BPF_PROG_TYPE_RAW_TRACEPOINT, or BPF_PROG_TYPE_SYSCALL), link_create() -> bpf_prog_attach_check_attach_type() hits the default branch: kernel/bpf/syscall.c:bpf_prog_attach_check_attach_type() { ... default: ptype = attach_type_to_prog_type(attach_type); if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) return -EINVAL; return 0; } Because attach_type_to_prog_type() never returns those program types for any attach_type, bpf_prog_attach_check_attach_type() returns -EINVAL and link_create() logs "Invalid attach_type.\n" instead of reaching the default branch of switch (prog->type) to log "Invalid prog type.\n". Second, for BPF_PROG_TYPE_CGROUP_SKB, bpf_prog_attach_check_attach_type() also performs a capability check: case BPF_PROG_TYPE_CGROUP_SKB: if (!bpf_token_capable(prog->aux->token, CAP_NET_ADMIN)) return -EPERM; When this check fails with -EPERM, link_create() still logs "Invalid attach_type.\n" even when attach_type is valid. Third, for BPF_PROG_TYPE_LSM and BPF_PROG_TYPE_TRACING, bpf_prog_attach_check_attach_type() only checks that attach_type maps to the general program type. The stricter expected_attach_type check happens inside switch (prog->type) in link_create(): case BPF_PROG_TYPE_LSM: case BPF_PROG_TYPE_TRACING: if (attr->link_create.attach_type != prog->expected_attach_type) { ret = -EINVAL; goto out; } If a caller passes an attach_type of the same program type that does not match prog->expected_attach_type, link_create() jumps to out without logging "Invalid attach_type.\n". Should the program type validation and attach_type logging be ordered so that unsupported program types, -EPERM failures, and expected_attach_type mismatches report accurate messages? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
