** Attachment added: "Test case for skipped syscall" https://bugs.launchpad.net/ubuntu/+source/linux-aws/+bug/1854573/+attachment/5308877/+files/sysemu_test.c
-- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux-aws in Ubuntu. https://bugs.launchpad.net/bugs/1854573 Title: Seccomp check skipped for syscall -1 in straced process and PTRACE_SYSEMU broken Status in linux-aws package in Ubuntu: New Bug description: If system call number -1 is called and the process is being traced with PTRACE_SYSCALL, for example by strace, the seccomp check is skipped and -ENOSYS is returned unconditionally (unless altered by the tracer), rather than carrying out action specified in the seccomp filter. The consequence of this is that it is not possible to reliably strace a seccomp based implementation of a foreign system call interface in which r7/x8 is permitted to be -1 on entry to a system call. I have traced this bug to commit f086f67485c5c126bcec4b0e96ac7319a2e59ab8 which attempts to implement PTRACE_SYSEMU. Contrary to x86-64 and the man ptrace page which states "For PTRACE_SYSEMU, continue and stop on entry to the next system call, which will not be executed.", on PTRACE_SYSEMU skips the current system call and stops on entry to the next system call. ProblemType: Bug DistroRelease: Ubuntu 19.10 Package: linux-image-5.3.0-1007-aws 5.3.0-1007.8 ProcVersionSignature: User Name 5.3.0-1007.8-aws 5.3.7 Uname: Linux 5.3.0-1007-aws aarch64 ApportVersion: 2.20.11-0ubuntu8.2 Architecture: arm64 Date: Sat Nov 30 13:38:28 2019 Ec2AMI: ami-0e88d70910be26319 Ec2AMIManifest: (unknown) Ec2AvailabilityZone: eu-west-1b Ec2InstanceType: a1.medium Ec2Kernel: unavailable Ec2Ramdisk: unavailable ProcEnviron: TERM=xterm-256color PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=C.UTF-8 SHELL=/bin/bash SourcePackage: linux-aws UpgradeStatus: Upgraded to eoan on 2019-11-09 (21 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-aws/+bug/1854573/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
