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Commit 39d637af authored by Dmitry Kasatkin's avatar Dmitry Kasatkin Committed by Mimi Zohar
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vfs: forbid write access when reading a file into memory 



This patch is based on top of the "vfs: support for a common kernel file
loader" patch set.  In general when the kernel is reading a file into
memory it does not want anything else writing to it.

The kernel currently only forbids write access to a file being executed.
This patch extends this locking to files being read by the kernel.

Changelog:
- moved function to kernel_read_file() - Mimi
- updated patch description - Mimi

Signed-off-by: default avatarDmitry Kasatkin <dmitry.kasatkin@huawei.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: default avatarMimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: default avatarLuis R. Rodriguez <mcgrof@kernel.org>
Acked-by: default avatarKees Cook <keescook@chromium.org>
parent da20dfe6

fs/exec.c

+21 −8
Original line number Diff line number Diff line
@@ -850,15 +850,25 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size, 
	if (ret)

		return ret;



	ret = deny_write_access(file);

	if (ret)

		return ret;



	i_size = i_size_read(file_inode(file));

	if (max_size > 0 && i_size > max_size)

		return -EFBIG;

	if (i_size <= 0)

		return -EINVAL;

	if (max_size > 0 && i_size > max_size) {

		ret = -EFBIG;

		goto out;

	}

	if (i_size <= 0) {

		ret = -EINVAL;

		goto out;

	}



	*buf = vmalloc(i_size);

	if (!*buf)

		return -ENOMEM;

	if (!*buf) {

		ret = -ENOMEM;

		goto out;

	}



	pos = 0;

	while (pos < i_size) {
@@ -876,18 +886,21 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size, 


	if (pos != i_size) {

		ret = -EIO;

		goto out;

		goto out_free;

	}



	ret = security_kernel_post_read_file(file, *buf, i_size, id);

	if (!ret)

		*size = pos;



out:

out_free:

	if (ret < 0) {

		vfree(*buf);

		*buf = NULL;

	}



out:

	allow_write_access(file);

	return ret;

}

EXPORT_SYMBOL_GPL(kernel_read_file);