From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dominik Brodowski Subject: [PATCH 24/45] kexec: call do_kexec_load() in compat syscall directly Date: Thu, 22 Mar 2018 10:00:38 +0100 Message-ID: <20180322090059.19361-25-linux@dominikbrodowski.net> References: <20180322090059.19361-1-linux@dominikbrodowski.net> Return-path: In-Reply-To: <20180322090059.19361-1-linux@dominikbrodowski.net> Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, viro@ZenIV.linux.org.uk, arnd@arndb.de, linux-arch@vger.kernel.org Cc: Eric Biederman , kexec@lists.infradead.org List-Id: linux-arch.vger.kernel.org do_kexec_load() can be called directly by compat_sys_kexec() as long as the same parameters checks are completed which are currently handled (also) by sys_kexec(). Therefore, move those to kexec_load_check(), call that newly introduced helper function from both sys_kexec() and compat_sys_kexec(), and duplicate the remaining code from sys_kexec() in compat_sys_kexec(). This patch is part of a series which tries to remove in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. Cc: Eric Biederman Cc: kexec@lists.infradead.org Signed-off-by: Dominik Brodowski --- kernel/kexec.c | 50 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 13 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index e62ec4dc6620..d959dc2c5587 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -192,11 +192,9 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, * that to happen you need to do that yourself. */ -SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, - struct kexec_segment __user *, segments, unsigned long, flags) +static inline int kexec_load_check(unsigned long nr_segments, + unsigned long flags) { - int result; - /* We only trust the superuser with rebooting the system. */ if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; @@ -208,17 +206,29 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) return -EINVAL; - /* Verify we are on the appropriate architecture */ - if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && - ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) - return -EINVAL; - /* Put an artificial cap on the number * of segments passed to kexec_load. */ if (nr_segments > KEXEC_SEGMENT_MAX) return -EINVAL; + return 0; +} + +SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, + struct kexec_segment __user *, segments, unsigned long, flags) +{ + int result; + + result = kexec_load_check(nr_segments, flags); + if (result) + return result; + + /* Verify we are on the appropriate architecture */ + if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && + ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) + return -EINVAL; + /* Because we write directly to the reserved memory * region when loading crash kernels we need a mutex here to * prevent multiple crash kernels from attempting to load @@ -247,15 +257,16 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, struct kexec_segment out, __user *ksegments; unsigned long i, result; + result = kexec_load_check(nr_segments, flags); + if (result) + return result; + /* Don't allow clients that don't understand the native * architecture to do anything. */ if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) return -EINVAL; - if (nr_segments > KEXEC_SEGMENT_MAX) - return -EINVAL; - ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); for (i = 0; i < nr_segments; i++) { result = copy_from_user(&in, &segments[i], sizeof(in)); @@ -272,6 +283,19 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, return -EFAULT; } - return sys_kexec_load(entry, nr_segments, ksegments, flags); + /* Because we write directly to the reserved memory + * region when loading crash kernels we need a mutex here to + * prevent multiple crash kernels from attempting to load + * simultaneously, and to prevent a crash kernel from loading + * over the top of a in use crash kernel. + * + * KISS: always take the mutex. + */ + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; + + result = do_kexec_load(entry, nr_segments, ksegments, flags); + + mutex_unlock(&kexec_mutex); } #endif -- 2.16.2 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from isilmar-4.linta.de ([136.243.71.142]:37684 "EHLO isilmar-4.linta.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752852AbeCVJBn (ORCPT ); Thu, 22 Mar 2018 05:01:43 -0400 From: Dominik Brodowski Subject: [PATCH 24/45] kexec: call do_kexec_load() in compat syscall directly Date: Thu, 22 Mar 2018 10:00:38 +0100 Message-ID: <20180322090059.19361-25-linux@dominikbrodowski.net> In-Reply-To: <20180322090059.19361-1-linux@dominikbrodowski.net> References: <20180322090059.19361-1-linux@dominikbrodowski.net> Sender: linux-arch-owner@vger.kernel.org List-ID: To: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, viro@ZenIV.linux.org.uk, arnd@arndb.de, linux-arch@vger.kernel.org Cc: Eric Biederman , kexec@lists.infradead.org Message-ID: <20180322090038.SEunJj2atrXk-HH80AEi1U4KQwfhMjsjAbJAw4wSNFs@z> do_kexec_load() can be called directly by compat_sys_kexec() as long as the same parameters checks are completed which are currently handled (also) by sys_kexec(). Therefore, move those to kexec_load_check(), call that newly introduced helper function from both sys_kexec() and compat_sys_kexec(), and duplicate the remaining code from sys_kexec() in compat_sys_kexec(). This patch is part of a series which tries to remove in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. Cc: Eric Biederman Cc: kexec@lists.infradead.org Signed-off-by: Dominik Brodowski --- kernel/kexec.c | 50 +++++++++++++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 13 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index e62ec4dc6620..d959dc2c5587 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -192,11 +192,9 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, * that to happen you need to do that yourself. */ -SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, - struct kexec_segment __user *, segments, unsigned long, flags) +static inline int kexec_load_check(unsigned long nr_segments, + unsigned long flags) { - int result; - /* We only trust the superuser with rebooting the system. */ if (!capable(CAP_SYS_BOOT) || kexec_load_disabled) return -EPERM; @@ -208,17 +206,29 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK)) return -EINVAL; - /* Verify we are on the appropriate architecture */ - if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && - ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) - return -EINVAL; - /* Put an artificial cap on the number * of segments passed to kexec_load. */ if (nr_segments > KEXEC_SEGMENT_MAX) return -EINVAL; + return 0; +} + +SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, + struct kexec_segment __user *, segments, unsigned long, flags) +{ + int result; + + result = kexec_load_check(nr_segments, flags); + if (result) + return result; + + /* Verify we are on the appropriate architecture */ + if (((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH) && + ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) + return -EINVAL; + /* Because we write directly to the reserved memory * region when loading crash kernels we need a mutex here to * prevent multiple crash kernels from attempting to load @@ -247,15 +257,16 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, struct kexec_segment out, __user *ksegments; unsigned long i, result; + result = kexec_load_check(nr_segments, flags); + if (result) + return result; + /* Don't allow clients that don't understand the native * architecture to do anything. */ if ((flags & KEXEC_ARCH_MASK) == KEXEC_ARCH_DEFAULT) return -EINVAL; - if (nr_segments > KEXEC_SEGMENT_MAX) - return -EINVAL; - ksegments = compat_alloc_user_space(nr_segments * sizeof(out)); for (i = 0; i < nr_segments; i++) { result = copy_from_user(&in, &segments[i], sizeof(in)); @@ -272,6 +283,19 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, return -EFAULT; } - return sys_kexec_load(entry, nr_segments, ksegments, flags); + /* Because we write directly to the reserved memory + * region when loading crash kernels we need a mutex here to + * prevent multiple crash kernels from attempting to load + * simultaneously, and to prevent a crash kernel from loading + * over the top of a in use crash kernel. + * + * KISS: always take the mutex. + */ + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; + + result = do_kexec_load(entry, nr_segments, ksegments, flags); + + mutex_unlock(&kexec_mutex); } #endif -- 2.16.2