Are you folks aware that: 'bpf: Move rcu lock management out of BPF_PROG_RUN routines' fixes a weird regression where sendmsg with an egress tc bpf program denying it was returning EFAULT instead of EPERM I've confirmed vanilla 5.18.0 is broken, and all it takes is cherrypicking that specific stable 5.18.x patch [ 710a8989b4b4067903f5b61314eda491667b6ab3 ] to fix behaviour. This was not a flaky failure... but a 100% reproducible behavioural breakage/failure in the test case at https://cs.android.com/android/platform/superproject/+/master:kernel/tests/net/test/bpf_test.py;l=517 (where 5.18 would return EFAULT instead of EPERM) --- A non standalone but perhaps useful (for reading) simplification of the test case follows. I was planning on reporting it, hence why I was trying to trim it down and have this ready anyway, only to discover it's already been fixed. But the commit message seems to be unrelated... some sort of compiler optimization shenanigans? Missing test case opportunity? Note: that I run this on x86_64 UML - that might matter?? #!/usr/bin/python # extracted snippet from AOSP, Apache2 licensed import csocket import cstruct import ctypes import errno import os import platform import socket import unittest __NR_bpf = { # pylint: disable=invalid-name "aarch64-32bit": 386, "aarch64-64bit": 280, "armv7l-32bit": 386, "armv8l-32bit": 386, "armv8l-64bit": 280, "i686-32bit": 357, "i686-64bit": 321, "x86_64-32bit": 357, "x86_64-64bit": 321, }[os.uname()[4] + "-" + platform.architecture()[0]] LOG_LEVEL = 1 LOG_SIZE = 65536 BPF_PROG_LOAD = 5 BPF_PROG_ATTACH = 8 BPF_PROG_DETACH = 9 BPF_PROG_TYPE_CGROUP_SKB = 8 BPF_CGROUP_INET_EGRESS = 1 BPF_REG_0 = 0 BPF_JMP = 0x05 BPF_K = 0x00 BPF_ALU64 = 0x07 BPF_MOV = 0xb0 BPF_EXIT = 0x90 BpfAttrProgLoad = cstruct.Struct( "bpf_attr_prog_load", "=IIQQIIQI", "prog_type insn_cnt insns" " license log_level log_size log_buf kern_version") BpfAttrProgAttach = cstruct.Struct( "bpf_attr_prog_attach", "=III", "target_fd attach_bpf_fd attach_type") BpfInsn = cstruct.Struct("bpf_insn", "=BBhi", "code dst_src_reg off imm") libc = ctypes.CDLL(ctypes.util.find_library("c"), use_errno=True) def BpfSyscall(op, attr): ret = libc.syscall(__NR_bpf, op, csocket.VoidPointer(attr), len(attr)) csocket.MaybeRaiseSocketError(ret) return ret def BpfProgLoad(prog_type, instructions, prog_license=b"GPL"): bpf_prog = "".join(instructions) insn_buff = ctypes.create_string_buffer(bpf_prog) gpl_license = ctypes.create_string_buffer(prog_license) log_buf = ctypes.create_string_buffer(b"", LOG_SIZE) return BpfSyscall(BPF_PROG_LOAD, BpfAttrProgLoad((prog_type, len(insn_buff) / len(BpfInsn), ctypes.addressof(insn_buff), ctypes.addressof(gpl_license), LOG_LEVEL, LOG_SIZE, ctypes.addressof(log_buf), 0))) # Attach a eBPF filter to a cgroup def BpfProgAttach(prog_fd, target_fd, prog_type): attr = BpfAttrProgAttach((target_fd, prog_fd, prog_type)) return BpfSyscall(BPF_PROG_ATTACH, attr) # Detach a eBPF filter from a cgroup def BpfProgDetach(target_fd, prog_type): attr = BpfAttrProgAttach((target_fd, 0, prog_type)) return BpfSyscall(BPF_PROG_DETACH, attr) class BpfCgroupEgressTest(unittest.TestCase): def setUp(self): self._cg_fd = os.open("/sys/fs/cgroup", os.O_DIRECTORY | os.O_RDONLY) BpfProgAttach(BpfProgLoad(BPF_PROG_TYPE_CGROUP_SKB, [ BpfInsn((BPF_ALU64 | BPF_MOV | BPF_K, BPF_REG_0, 0, 0)).Pack(), # Mov64Imm(REG0, 0) BpfInsn((BPF_JMP | BPF_EXIT, 0, 0, 0)).Pack() # Exit ]), self._cg_fd, BPF_CGROUP_INET_EGRESS) def tearDown(self): BpfProgDetach(self._cg_fd, BPF_CGROUP_INET_EGRESS) os.close(self._cg_fd) def testCgroupEgressBlocked(self): s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, 0) s.bind(("127.0.0.1", 0)) addr = s.getsockname() # previously: s.sendto("foo", addr) would fail with EPERM, but on 5.18+ it EFAULTs self.assertRaisesRegexp(EnvironmentError, os.strerror(errno.EFAULT), s.sendto, "foo", addr) if __name__ == "__main__": unittest.main()
