Revision ec057595cb3fb339e692898bedccd566160ba086 authored by Linus Torvalds on 06 December 2019, 20:40:35 UTC, committed by Linus Torvalds on 06 December 2019, 20:40:35 UTC
Similarly to commit 8f868d68d335 ("pipe: Fix missing mask update after pipe_wait()") this fixes a case where the pipe rewrite ended up caching the pipe state incorrectly over a pipe lock drop event. It wasn't quite as obvious, because you needed to splice data from a pipe to a file, which is a fairly unusual operation, but it's completely wrong. Make sure we load the pipe head/tail/size information only after we've waited for there to be data in the pipe. While in that file, also make one of the splice helper functions use the canonical arghument order for pipe_empty(). That's syntactic - pipe emptiness is just that head and tail are equal, and thus mixing up head and tail doesn't really matter. It's still wrong, though. Reported-by: David Sterba <dsterba@suse.cz> Cc: David Howells <dhowells@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 7ada90e
kexec.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 copy_user_segment_list(struct kimage *image,
unsigned long nr_segments,
struct kexec_segment __user *segments)
{
int ret;
size_t segment_bytes;
/* Read in the segments */
image->nr_segments = nr_segments;
segment_bytes = nr_segments * sizeof(*segments);
ret = copy_from_user(image->segment, segments, segment_bytes);
if (ret)
ret = -EFAULT;
return ret;
}
static int kimage_alloc_init(struct kimage **rimage, unsigned long entry,
unsigned long nr_segments,
struct kexec_segment __user *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;
ret = copy_user_segment_list(image, nr_segments, segments);
if (ret)
goto out_free_image;
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 __user *segments, unsigned long flags)
{
struct kimage **dest_image, *image;
unsigned long i;
int ret;
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));
return 0;
}
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)
return ret;
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);
/* 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);
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);
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)
{
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
* 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, segments, flags);
mutex_unlock(&kexec_mutex);
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 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;
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));
if (result)
return -EFAULT;
out.buf = compat_ptr(in.buf);
out.bufsz = in.bufsz;
out.mem = in.mem;
out.memsz = in.memsz;
result = copy_to_user(&ksegments[i], &out, sizeof(out));
if (result)
return -EFAULT;
}
/* 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
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