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![Pasha Tatashin](/assets/img/avatar_default.png)
Patch series "Allow to kexec with initramfs larger than 2G", v2. Currently, the largest initramfs that is supported by kexec_file_load() syscall is 2G. This is because kernel_read_file() returns int, and is limited to INT_MAX or 2G. On the other hand, there are kexec based boot loaders (i.e. u-root), that may need to boot netboot images that might be larger than 2G. The first patch changes the return type from int to ssize_t in kernel_read_file* functions. The second patch increases the maximum initramfs file size to 4G. Tested: verified that can kexec_file_load() works with 4G initramfs on x86_64. This patch (of 2): Currently, the maximum file size that is supported is 2G. This may be too small in some cases. For example, kexec_file_load() system call loads initramfs. In some netboot cases initramfs can be rather large. Allow to use up-to ssize_t bytes. The callers still can limit the maximum file size via buf_size. Link: https://lkml.kernel.org/r/20220527025535.3953665-1-pasha.tatashin@soleen.com Link: https://lkml.kernel.org/r/20220527025535.3953665-2-pasha.tatashin@soleen.com Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Baoquan He <bhe@redhat.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Greg Thelen <gthelen@google.com> Cc: Sasha Levin <sashal@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
189 lines
4.4 KiB
C
189 lines
4.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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#include <linux/fs.h>
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#include <linux/fs_struct.h>
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#include <linux/kernel_read_file.h>
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#include <linux/security.h>
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#include <linux/vmalloc.h>
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/**
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* kernel_read_file() - read file contents into a kernel buffer
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*
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* @file file to read from
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* @offset where to start reading from (see below).
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* @buf pointer to a "void *" buffer for reading into (if
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* *@buf is NULL, a buffer will be allocated, and
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* @buf_size will be ignored)
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* @buf_size size of buf, if already allocated. If @buf not
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* allocated, this is the largest size to allocate.
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* @file_size if non-NULL, the full size of @file will be
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* written here.
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* @id the kernel_read_file_id identifying the type of
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* file contents being read (for LSMs to examine)
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*
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* @offset must be 0 unless both @buf and @file_size are non-NULL
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* (i.e. the caller must be expecting to read partial file contents
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* via an already-allocated @buf, in at most @buf_size chunks, and
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* will be able to determine when the entire file was read by
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* checking @file_size). This isn't a recommended way to read a
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* file, though, since it is possible that the contents might
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* change between calls to kernel_read_file().
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*
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* Returns number of bytes read (no single read will be bigger
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* than SSIZE_MAX), or negative on error.
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*
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*/
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ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
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size_t buf_size, size_t *file_size,
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enum kernel_read_file_id id)
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{
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loff_t i_size, pos;
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ssize_t copied;
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void *allocated = NULL;
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bool whole_file;
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int ret;
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if (offset != 0 && (!*buf || !file_size))
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return -EINVAL;
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if (!S_ISREG(file_inode(file)->i_mode))
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return -EINVAL;
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ret = deny_write_access(file);
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if (ret)
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return ret;
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i_size = i_size_read(file_inode(file));
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if (i_size <= 0) {
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ret = -EINVAL;
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goto out;
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}
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/* The file is too big for sane activities. */
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if (i_size > SSIZE_MAX) {
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ret = -EFBIG;
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goto out;
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}
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/* The entire file cannot be read in one buffer. */
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if (!file_size && offset == 0 && i_size > buf_size) {
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ret = -EFBIG;
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goto out;
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}
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whole_file = (offset == 0 && i_size <= buf_size);
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ret = security_kernel_read_file(file, id, whole_file);
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if (ret)
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goto out;
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if (file_size)
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*file_size = i_size;
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if (!*buf)
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*buf = allocated = vmalloc(i_size);
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if (!*buf) {
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ret = -ENOMEM;
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goto out;
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}
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pos = offset;
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copied = 0;
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while (copied < buf_size) {
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ssize_t bytes;
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size_t wanted = min_t(size_t, buf_size - copied,
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i_size - pos);
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bytes = kernel_read(file, *buf + copied, wanted, &pos);
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if (bytes < 0) {
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ret = bytes;
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goto out_free;
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}
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if (bytes == 0)
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break;
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copied += bytes;
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}
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if (whole_file) {
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if (pos != i_size) {
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ret = -EIO;
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goto out_free;
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}
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ret = security_kernel_post_read_file(file, *buf, i_size, id);
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}
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out_free:
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if (ret < 0) {
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if (allocated) {
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vfree(*buf);
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*buf = NULL;
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}
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}
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out:
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allow_write_access(file);
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return ret == 0 ? copied : ret;
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}
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EXPORT_SYMBOL_GPL(kernel_read_file);
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ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
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size_t buf_size, size_t *file_size,
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enum kernel_read_file_id id)
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{
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struct file *file;
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ssize_t ret;
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if (!path || !*path)
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return -EINVAL;
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file = filp_open(path, O_RDONLY, 0);
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if (IS_ERR(file))
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return PTR_ERR(file);
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ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
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fput(file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
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ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
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void **buf, size_t buf_size,
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size_t *file_size,
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enum kernel_read_file_id id)
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{
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struct file *file;
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struct path root;
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ssize_t ret;
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if (!path || !*path)
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return -EINVAL;
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task_lock(&init_task);
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get_fs_root(init_task.fs, &root);
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task_unlock(&init_task);
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file = file_open_root(&root, path, O_RDONLY, 0);
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path_put(&root);
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if (IS_ERR(file))
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return PTR_ERR(file);
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ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
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fput(file);
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return ret;
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}
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EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
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ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
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size_t buf_size, size_t *file_size,
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enum kernel_read_file_id id)
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{
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struct fd f = fdget(fd);
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ssize_t ret = -EBADF;
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if (!f.file || !(f.file->f_mode & FMODE_READ))
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goto out;
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ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id);
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out:
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fdput(f);
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return ret;
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}
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EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);
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