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[173.79.56.208]) by smtp.gmail.com with ESMTPSA id y2-20020a05620a44c200b006e42a8e9f9bsm14128630qkp.121.2023.01.21.02.23.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 21 Jan 2023 02:23:21 -0800 (PST) From: Gregory Price X-Google-Original-From: Gregory Price To: linux-kernel@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, krisman@collabora.com, tglx@linutronix.de, luto@kernel.org, oleg@redhat.com, peterz@infradead.org, ebiederm@xmission.com, akpm@linux-foundation.org, adobriyan@gmail.com, corbet@lwn.net, shuah@kernel.org, Gregory Price Subject: [PATCH v4 1/3] ptrace,syscall_user_dispatch: Implement Syscall User Dispatch Suspension Date: Sat, 21 Jan 2023 05:23:14 -0500 Message-Id: <20230121102316.331935-2-gregory.price@memverge.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230121102316.331935-1-gregory.price@memverge.com> References: <20230121102316.331935-1-gregory.price@memverge.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org Adds PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH to ptrace options, and modify Syscall User Dispatch to suspend interception when enabled. This is modeled after the SUSPEND_SECCOMP feature, which suspends SECCOMP interposition. Without doing this, software like CRIU will inject system calls into a process and be intercepted by Syscall User Dispatch, either causing a crash (due to blocked signals) or the delivery of those signals to a ptracer (not the intended behavior). Since Syscall User Dispatch is not a privileged feature, a check for permissions is not required, however attempting to set this option when CONFIG_CHECKPOINT_RESTORE it not supported should be disallowed, as its intended use is checkpoint/resume. Signed-off-by: Gregory Price Acked-by: Peter Zijlstra (Intel) --- include/linux/ptrace.h | 2 ++ include/uapi/linux/ptrace.h | 6 +++++- kernel/entry/syscall_user_dispatch.c | 5 +++++ kernel/ptrace.c | 4 ++++ 4 files changed, 16 insertions(+), 1 deletion(-) diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index eaaef3ffec22..461ae5c99d57 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -45,6 +45,8 @@ extern int ptrace_access_vm(struct task_struct *tsk, unsigned long addr, #define PT_EXITKILL (PTRACE_O_EXITKILL << PT_OPT_FLAG_SHIFT) #define PT_SUSPEND_SECCOMP (PTRACE_O_SUSPEND_SECCOMP << PT_OPT_FLAG_SHIFT) +#define PT_SUSPEND_SYSCALL_USER_DISPATCH \ + (PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH << PT_OPT_FLAG_SHIFT) extern long arch_ptrace(struct task_struct *child, long request, unsigned long addr, unsigned long data); diff --git a/include/uapi/linux/ptrace.h b/include/uapi/linux/ptrace.h index 195ae64a8c87..ba9e3f19a22c 100644 --- a/include/uapi/linux/ptrace.h +++ b/include/uapi/linux/ptrace.h @@ -146,9 +146,13 @@ struct ptrace_rseq_configuration { /* eventless options */ #define PTRACE_O_EXITKILL (1 << 20) #define PTRACE_O_SUSPEND_SECCOMP (1 << 21) +#define PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH (1 << 22) #define PTRACE_O_MASK (\ - 0x000000ff | PTRACE_O_EXITKILL | PTRACE_O_SUSPEND_SECCOMP) + 0x000000ff | \ + PTRACE_O_EXITKILL | \ + PTRACE_O_SUSPEND_SECCOMP | \ + PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH) #include diff --git a/kernel/entry/syscall_user_dispatch.c b/kernel/entry/syscall_user_dispatch.c index 0b6379adff6b..b5ec75164805 100644 --- a/kernel/entry/syscall_user_dispatch.c +++ b/kernel/entry/syscall_user_dispatch.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include @@ -36,6 +37,10 @@ bool syscall_user_dispatch(struct pt_regs *regs) struct syscall_user_dispatch *sd = ¤t->syscall_dispatch; char state; + if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) && + unlikely(current->ptrace & PT_SUSPEND_SYSCALL_USER_DISPATCH)) + return false; + if (likely(instruction_pointer(regs) - sd->offset < sd->len)) return false; diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 54482193e1ed..a348b68d07a2 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -370,6 +370,10 @@ static int check_ptrace_options(unsigned long data) if (data & ~(unsigned long)PTRACE_O_MASK) return -EINVAL; + if (unlikely(data & PTRACE_O_SUSPEND_SYSCALL_USER_DISPATCH) && + (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE))) + return -EINVAL; + if (unlikely(data & PTRACE_O_SUSPEND_SECCOMP)) { if (!IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) || !IS_ENABLED(CONFIG_SECCOMP))