Date: Thu, 28 Jan 2016 18:33:01 -0800 From: Andy Lutomirski <luto@...capital.net> To: Kees Cook <keescook@...omium.org> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, jeffv@...gle.com, Oleg Nesterov <oleg@...hat.com>, Will Drewry <wad@...omium.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>, Linux API <linux-api@...r.kernel.org>, LSM List <linux-security-module@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [RFC][PATCH] seccomp: add SECCOMP_RET_ACK for non-fatal SIGSYS On Thu, Jan 28, 2016 at 5:06 PM, Kees Cook <keescook@...omium.org> wrote: > Tracing processes for syscall usage can be done one step at a time with > SECCOMP_RET_TRAP, but this will block the syscall. Alternatively, using > a ptrace manager to handle SECCOMP_RET_TRACE returns can be used but is > heavy weight and depends on the ptrace infrastructure. A light-weight > method to learn syscalls is needed, which can reuse the existing delivery > of SIGSYS but without skipping the syscall. This is implemented as > SECCOMP_RET_ACK which is as permissive as SECCOMP_RET_ALLOW but delivers > SIGSYS after syscall completion, as long as the SECCOMP_RET_DATA is > non-zero. A signal handler can install a new rule for each syscall as > they are signaled with SECCOMP_RET_DATA set to 0 to disable reporting > for that syscall in the future (which is required for restarting syscalls > that are signal-sensitive like nanosleep). > > Registers from the signal will reflect registers after the syscall returns > rather than before. Signal-sensitive syscalls will trigger EINTR, so they > must be whitelisted before they are resumed. Not allowing the sigreturn > syscall (and likely prctl to whitelist) will make using SECCOMP_RET_ACK > useless. > > Signed-off-by: Kees Cook <keescook@...omium.org> Could this use task_work to queue the signal on return to user mode instead? Would that solve the EINTR issues? --Andy
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