1*7304104dSAndroid Build Coastguard Worker# When yama is enabled in the kernel it might be used to filter any user 2*7304104dSAndroid Build Coastguard Worker# space access which requires PTRACE_MODE_ATTACH like ptrace attach, access 3*7304104dSAndroid Build Coastguard Worker# to /proc/PID/{mem,personality,stack,syscall}, and the syscalls 4*7304104dSAndroid Build Coastguard Worker# process_vm_readv and process_vm_writev which are used for interprocess 5*7304104dSAndroid Build Coastguard Worker# services, communication and introspection (like synchronisation, signaling, 6*7304104dSAndroid Build Coastguard Worker# debugging, tracing and profiling) of processes. 7*7304104dSAndroid Build Coastguard Worker# 8*7304104dSAndroid Build Coastguard Worker# Usage of ptrace attach is restricted by normal user permissions. Normal 9*7304104dSAndroid Build Coastguard Worker# unprivileged processes cannot interact through ptrace with processes 10*7304104dSAndroid Build Coastguard Worker# that they cannot send signals to or processes that are running set-uid 11*7304104dSAndroid Build Coastguard Worker# or set-gid. 12*7304104dSAndroid Build Coastguard Worker# 13*7304104dSAndroid Build Coastguard Worker# yama ptrace scope can be used to reduce these permissions even more. 14*7304104dSAndroid Build Coastguard Worker# This should normally not be done because it will break various programs 15*7304104dSAndroid Build Coastguard Worker# relying on the default ptrace security restrictions. But can be used 16*7304104dSAndroid Build Coastguard Worker# if you don't have any other way to separate processes in their own 17*7304104dSAndroid Build Coastguard Worker# domains. A different way to restrict ptrace is to set the selinux 18*7304104dSAndroid Build Coastguard Worker# deny_ptrace boolean. Both mechanisms will break some programs relying 19*7304104dSAndroid Build Coastguard Worker# on the ptrace system call and might force users to elevate their 20*7304104dSAndroid Build Coastguard Worker# privileges to root to do their work. 21*7304104dSAndroid Build Coastguard Worker# 22*7304104dSAndroid Build Coastguard Worker# For more information see Documentation/security/Yama.txt in the kernel 23*7304104dSAndroid Build Coastguard Worker# sources. Which also describes the defaults when CONFIG_SECURITY_YAMA 24*7304104dSAndroid Build Coastguard Worker# is enabled in a kernel build (currently 1 for ptrace_scope). 25*7304104dSAndroid Build Coastguard Worker# 26*7304104dSAndroid Build Coastguard Worker# This runtime kernel parameter can be set to the following options: 27*7304104dSAndroid Build Coastguard Worker# (Note that setting this to anything except zero will break programs!) 28*7304104dSAndroid Build Coastguard Worker# 29*7304104dSAndroid Build Coastguard Worker# 0 - Default attach security permissions. 30*7304104dSAndroid Build Coastguard Worker# 1 - Restricted attach. Only child processes plus normal permissions. 31*7304104dSAndroid Build Coastguard Worker# 2 - Admin-only attach. Only executables with CAP_SYS_PTRACE. 32*7304104dSAndroid Build Coastguard Worker# 3 - No attach. No process may call ptrace at all. Irrevocable. 33*7304104dSAndroid Build Coastguard Worker# 34*7304104dSAndroid Build Coastguard Workerkernel.yama.ptrace_scope = 0 35*7304104dSAndroid Build Coastguard Worker 36