forked from Minki/linux
113eeb5177
In preparation for further refactoring of kernel_read_file*(), rename the "max_size" argument to the more accurate "buf_size", and correct its type to size_t. Add kerndoc to explain the specifics of how the arguments will be used. Note that with buf_size now size_t, it can no longer be negative (and was never called with a negative value). Adjust callers to use it as a "maximum size" when *buf is NULL. Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com> Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> Reviewed-by: James Morris <jamorris@linux.microsoft.com> Acked-by: Scott Branden <scott.branden@broadcom.com> Link: https://lore.kernel.org/r/20201002173828.2099543-7-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
153 lines
3.1 KiB
C
153 lines
3.1 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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* @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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* @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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* Returns number of bytes read (no single read will be bigger
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* than INT_MAX), or negative on error.
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*
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*/
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int kernel_read_file(struct file *file, void **buf,
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size_t buf_size, 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 bytes = 0;
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void *allocated = NULL;
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int ret;
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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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ret = security_kernel_read_file(file, id);
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if (ret)
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goto out;
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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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if (i_size > INT_MAX || i_size > buf_size) {
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ret = -EFBIG;
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goto out;
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}
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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 = 0;
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while (pos < i_size) {
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bytes = kernel_read(file, *buf + pos, i_size - pos, &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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}
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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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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 ? pos : ret;
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}
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EXPORT_SYMBOL_GPL(kernel_read_file);
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int kernel_read_file_from_path(const char *path, void **buf,
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size_t buf_size, enum kernel_read_file_id id)
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{
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struct file *file;
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int 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, buf, buf_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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int kernel_read_file_from_path_initns(const char *path, void **buf,
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size_t buf_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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int 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.dentry, root.mnt, 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, buf, buf_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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int kernel_read_file_from_fd(int fd, void **buf, size_t buf_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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int ret = -EBADF;
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if (!f.file)
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goto out;
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ret = kernel_read_file(f.file, buf, buf_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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