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 removes in-kernel calls to syscalls. On this basis, the syscall entry path can be streamlined. For details, see http://lkml.kernel.org/r/20180325162527.GA17492@xxxxxxxxxxxxxxxxxxxxxxxxxx Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: kexec@xxxxxxxxxxxxxxxxxxx Signed-off-by: Dominik Brodowski <linux@xxxxxxxxxxxxxxxxxxxx> --- kernel/kexec.c | 52 +++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 39 insertions(+), 13 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index e62ec4dc6620..aed8fb2564b3 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 +283,21 @@ 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); + + return result; } #endif -- 2.16.3
