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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id mg17sm602086pjb.17.2021.11.18.15.54.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Nov 2021 15:54:03 -0800 (PST) Date: Thu, 18 Nov 2021 15:54:02 -0800 From: Kees Cook To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, Kyle Huey , Linus Torvalds , Andrea Righi , Shuah Khan , Alexei Starovoitov , Andy Lutomirski , Will Drewry , "open list:KERNEL SELFTEST FRAMEWORK" , bpf , linux-hardening@vger.kernel.org, Robert O'Callahan , Oliver Sang , lkp@lists.01.org, lkp@intel.com Subject: Re: [PATCH 1/2] signal: Don't always set SA_IMMUTABLE for forced signals Message-ID: <202111181553.A4FDEB1@keescook> References: <87k0h6334w.fsf@email.froward.int.ebiederm.org> <202111171341.41053845C3@keescook> <202111171728.D85A4E2571@keescook> <87h7c9qg7p.fsf_-_@email.froward.int.ebiederm.org> <877dd5qfw5.fsf_-_@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <877dd5qfw5.fsf_-_@email.froward.int.ebiederm.org> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Thu, Nov 18, 2021 at 04:04:58PM -0600, Eric W. Biederman wrote: > > Recently to prevent issues with SECCOMP_RET_KILL and similar signals > being changed before they are delivered SA_IMMUTABLE was added. > > Unfortunately this broke debuggers[1][2] which reasonably expect to be > able to trap synchronous SIGTRAP and SIGSEGV even when the target > process is not configured to handle those signals. > > Update force_sig_to_task to support both the case when we can > allow the debugger to intercept and possibly ignore the > signal and the case when it is not safe to let userspace > known about the signal until the process has exited. > > Reported-by: Kyle Huey > Reported-by: kernel test robot > Cc: stable@vger.kernel.org > [1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com > [2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-902 > Fixes: 00b06da29cf9 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed") > Signed-off-by: "Eric W. Biederman" > --- > kernel/signal.c | 23 ++++++++++++++++------- > 1 file changed, 16 insertions(+), 7 deletions(-) > > diff --git a/kernel/signal.c b/kernel/signal.c > index 7c4b7ae714d4..02058c983bd6 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1298,6 +1298,12 @@ int do_send_sig_info(int sig, struct kernel_siginfo *info, struct task_struct *p > return ret; > } > > +enum sig_handler { > + HANDLER_CURRENT, /* If reachable use the current handler */ > + HANDLER_SIG_DFL, /* Always use SIG_DFL handler semantics */ > + HANDLER_EXIT, /* Only visible as the proces exit code */ Oh, I just noticed this typo "proces" -> "process" -Kees -- Kees Cook