linux-stable/kernel/kexec.c
Arnd Bergmann 5d700a0fd7 kexec: avoid compat_alloc_user_space
kimage_alloc_init() expects a __user pointer, so compat_sys_kexec_load()
uses compat_alloc_user_space() to convert the layout and put it back onto
the user space caller stack.

Moving the user space access into the syscall handler directly actually
makes the code simpler, as the conversion for compat mode can now be done
on kernel memory.

Link: https://lkml.kernel.org/r/20210727144859.4150043-3-arnd@kernel.org
Link: https://lore.kernel.org/lkml/YPbtsU4GX6PL7%2F42@infradead.org/
Link: https://lore.kernel.org/lkml/m1y2cbzmnw.fsf@fess.ebiederm.org/
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Co-developed-by: Eric Biederman <ebiederm@xmission.com>
Co-developed-by: Christoph Hellwig <hch@infradead.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Feng Tang <feng.tang@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-09-08 15:32:34 -07:00

298 lines
7.4 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* kexec.c - kexec_load system call
* Copyright (C) 2002-2004 Eric Biederman <ebiederm@xmission.com>
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/capability.h>
#include <linux/mm.h>
#include <linux/file.h>
#include <linux/security.h>
#include <linux/kexec.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/syscalls.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include "kexec_internal.h"
static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
unsigned long nr_segments,
struct kexec_segment *segments,
unsigned long flags)
{
int ret;
struct kimage *image;
bool kexec_on_panic = flags & KEXEC_ON_CRASH;
if (kexec_on_panic) {
/* Verify we have a valid entry point */
if ((entry < phys_to_boot_phys(crashk_res.start)) ||
(entry > phys_to_boot_phys(crashk_res.end)))
return -EADDRNOTAVAIL;
}
/* Allocate and initialize a controlling structure */
image = do_kimage_alloc_init();
if (!image)
return -ENOMEM;
image->start = entry;
image->nr_segments = nr_segments;
memcpy(image->segment, segments, nr_segments * sizeof(*segments));
if (kexec_on_panic) {
/* Enable special crash kernel control page alloc policy. */
image->control_page = crashk_res.start;
image->type = KEXEC_TYPE_CRASH;
}
ret = sanity_check_segment_list(image);
if (ret)
goto out_free_image;
/*
* Find a location for the control code buffer, and add it
* the vector of segments so that it's pages will also be
* counted as destination pages.
*/
ret = -ENOMEM;
image->control_code_page = kimage_alloc_control_pages(image,
get_order(KEXEC_CONTROL_PAGE_SIZE));
if (!image->control_code_page) {
pr_err("Could not allocate control_code_buffer\n");
goto out_free_image;
}
if (!kexec_on_panic) {
image->swap_page = kimage_alloc_control_pages(image, 0);
if (!image->swap_page) {
pr_err("Could not allocate swap buffer\n");
goto out_free_control_pages;
}
}
*rimage = image;
return 0;
out_free_control_pages:
kimage_free_page_list(&image->control_pages);
out_free_image:
kfree(image);
return ret;
}
static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
struct kexec_segment *segments, unsigned long flags)
{
struct kimage **dest_image, *image;
unsigned long i;
int ret;
/*
* 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;
if (flags & KEXEC_ON_CRASH) {
dest_image = &kexec_crash_image;
if (kexec_crash_image)
arch_kexec_unprotect_crashkres();
} else {
dest_image = &kexec_image;
}
if (nr_segments == 0) {
/* Uninstall image */
kimage_free(xchg(dest_image, NULL));
ret = 0;
goto out_unlock;
}
if (flags & KEXEC_ON_CRASH) {
/*
* Loading another kernel to switch to if this one
* crashes. Free any current crash dump kernel before
* we corrupt it.
*/
kimage_free(xchg(&kexec_crash_image, NULL));
}
ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags);
if (ret)
goto out_unlock;
if (flags & KEXEC_PRESERVE_CONTEXT)
image->preserve_context = 1;
ret = machine_kexec_prepare(image);
if (ret)
goto out;
/*
* Some architecture(like S390) may touch the crash memory before
* machine_kexec_prepare(), we must copy vmcoreinfo data after it.
*/
ret = kimage_crash_copy_vmcoreinfo(image);
if (ret)
goto out;
for (i = 0; i < nr_segments; i++) {
ret = kimage_load_segment(image, &image->segment[i]);
if (ret)
goto out;
}
kimage_terminate(image);
ret = machine_kexec_post_load(image);
if (ret)
goto out;
/* Install the new kernel and uninstall the old */
image = xchg(dest_image, image);
out:
if ((flags & KEXEC_ON_CRASH) && kexec_crash_image)
arch_kexec_protect_crashkres();
kimage_free(image);
out_unlock:
mutex_unlock(&kexec_mutex);
return ret;
}
/*
* Exec Kernel system call: for obvious reasons only root may call it.
*
* This call breaks up into three pieces.
* - A generic part which loads the new kernel from the current
* address space, and very carefully places the data in the
* allocated pages.
*
* - A generic part that interacts with the kernel and tells all of
* the devices to shut down. Preventing on-going dmas, and placing
* the devices in a consistent state so a later kernel can
* reinitialize them.
*
* - A machine specific part that includes the syscall number
* and then copies the image to it's final destination. And
* jumps into the image at entry.
*
* kexec does not sync, or unmount filesystems so if you need
* that to happen you need to do that yourself.
*/
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;
/* Permit LSMs and IMA to fail the kexec */
result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false);
if (result < 0)
return result;
/*
* kexec can be used to circumvent module loading restrictions, so
* prevent loading in that case
*/
result = security_locked_down(LOCKDOWN_KEXEC);
if (result)
return result;
/*
* Verify we have a legal set of flags
* This leaves us room for future extensions.
*/
if ((flags & KEXEC_FLAGS) != (flags & ~KEXEC_ARCH_MASK))
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)
{
struct kexec_segment *ksegments;
unsigned long 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;
ksegments = memdup_user(segments, nr_segments * sizeof(ksegments[0]));
if (IS_ERR(ksegments))
return PTR_ERR(ksegments);
result = do_kexec_load(entry, nr_segments, ksegments, flags);
kfree(ksegments);
return result;
}
#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
compat_ulong_t, nr_segments,
struct compat_kexec_segment __user *, segments,
compat_ulong_t, flags)
{
struct compat_kexec_segment in;
struct kexec_segment *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;
ksegments = kmalloc_array(nr_segments, sizeof(ksegments[0]),
GFP_KERNEL);
if (!ksegments)
return -ENOMEM;
for (i = 0; i < nr_segments; i++) {
result = copy_from_user(&in, &segments[i], sizeof(in));
if (result)
goto fail;
ksegments[i].buf = compat_ptr(in.buf);
ksegments[i].bufsz = in.bufsz;
ksegments[i].mem = in.mem;
ksegments[i].memsz = in.memsz;
}
result = do_kexec_load(entry, nr_segments, ksegments, flags);
fail:
kfree(ksegments);
return result;
}
#endif