Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Medium] bpf: misreported attach_type and prog_type errors in link_create() --
commit 64df6223de5ef67537b774b5db553b0530d3bf6e Author: Leon Hwang <[email protected]> bpf: Add syscall common attrs support for link_create This commit adds syscall common attributes support to link_create() so that an internal verifier log instance is created and finalized to report error messages for invalid prog_fd, invalid attach_type, and invalid prog type. Link: https://lore.kernel.org/bpf/[email protected]/ > diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c > index 849bc9136299d..61d100e794b45 100644 > --- a/kernel/bpf/syscall.c > +++ b/kernel/bpf/syscall.c > @@ -5856,8 +5856,11 @@ 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; > > @@ -5867,14 +5870,24 @@ 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: > @@ -5953,12 +5966,19 @@ 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 checking prog->type in link_create() cause unsupported program types and permission errors to be misreported as "Invalid attach_type." instead of reaching the default "Invalid prog type." branch? In kernel/bpf/syscall.c, bpf_prog_attach_check_attach_type() handles any prog->type not explicitly listed in its switch via: kernel/bpf/syscall.c:bpf_prog_attach_check_attach_type() { ... case BPF_PROG_TYPE_CGROUP_SKB: if (!bpf_token_capable(prog->aux->token, CAP_NET_ADMIN)) return -EPERM; ... default: ptype = attach_type_to_prog_type(attach_type); if (ptype == BPF_PROG_TYPE_UNSPEC || ptype != prog->type) return -EINVAL; return 0; } This leads to three cases where the logged message does not match the actual failure: 1. When a caller passes a valid prog_fd for an unsupported program type (such as BPF_PROG_TYPE_SOCKET_FILTER, BPF_PROG_TYPE_SCHED_ACT, BPF_PROG_TYPE_RAW_TRACEPOINT, or BPF_PROG_TYPE_SYSCALL), attach_type_to_prog_type() never returns that prog->type. As a result, bpf_prog_attach_check_attach_type() returns -EINVAL, and link_create() logs "Invalid attach_type.\n" and jumps to out, leaving the default "Invalid prog type.\n" branch unreachable for almost all unsupported program types (except BPF_PROG_TYPE_LIRC_MODE2 when CONFIG_NET=y, or networking types when CONFIG_NET=n). 2. For BPF_PROG_TYPE_CGROUP_SKB, bpf_prog_attach_check_attach_type() checks !bpf_token_capable(prog->aux->token, CAP_NET_ADMIN) and returns -EPERM. Because link_create() unconditionally logs "Invalid attach_type.\n" whenever bpf_prog_attach_check_attach_type() returns non-zero, a permission failure with a valid attach_type also logs "Invalid attach_type.\n". 3. Conversely, for BPF_PROG_TYPE_LSM and BPF_PROG_TYPE_TRACING, bpf_prog_attach_check_attach_type() only verifies that attach_type_to_prog_type(attach_type) == prog->type. If a caller passes an attach_type in the same family that does not match prog->expected_attach_type (for example, BPF_TRACE_FEXIT for a BPF_TRACE_FENTRY program), it passes bpf_prog_attach_check_attach_type() and fails later 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; } which jumps to out without logging "Invalid attach_type.\n". [ ... ] > return ret; > } [ ... ] > > -- > 2.51.2 > -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
