Commit 2949ad50 authored by Vasiliy Kulikov's avatar Vasiliy Kulikov Committed by Rafael J. Wysocki
Browse files

ACPI / debugfs: Fix buffer overflows, double free 



File position is not controlled, it may lead to overwrites of arbitrary
kernel memory.  Also the code may kfree() the same pointer multiple
times.

One more flaw is still present: if multiple processes open the file then
all 3 static variables are shared, leading to various race conditions.
They should be moved to file->private_data.

Signed-off-by: default avatarVasiliy Kulikov <segoon@openwall.com>
Reviewed-by: default avatarWANG Cong <xiyou.wangcong@gmail.com>
Reviewed-by: default avatarEugene Teo <eugeneteo@kernel.org>
Cc: stable@kernel.org
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
parent 2aa15890

drivers/acpi/debugfs.c

+14 −6
Original line number Diff line number Diff line
@@ -26,7 +26,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, 
			size_t count, loff_t *ppos)

{

	static char *buf;

	static int uncopied_bytes;

	static u32 max_size;

	static u32 uncopied_bytes;



	struct acpi_table_header table;

	acpi_status status;
@@ -37,19 +39,24 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, 
		if (copy_from_user(&table, user_buf,

				   sizeof(struct acpi_table_header)))

			return -EFAULT;

		uncopied_bytes = table.length;

		buf = kzalloc(uncopied_bytes, GFP_KERNEL);

		uncopied_bytes = max_size = table.length;

		buf = kzalloc(max_size, GFP_KERNEL);

		if (!buf)

			return -ENOMEM;

	}



	if (uncopied_bytes < count) {

		kfree(buf);

	if (buf == NULL)

		return -EINVAL;



	if ((*ppos > max_size) ||

	    (*ppos + count > max_size) ||

	    (*ppos + count < count) ||

	    (count > uncopied_bytes))

		return -EINVAL;

	}



	if (copy_from_user(buf + (*ppos), user_buf, count)) {

		kfree(buf);

		buf = NULL;

		return -EFAULT;

	}
@@ -59,6 +66,7 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, 
	if (!uncopied_bytes) {

		status = acpi_install_method(buf);

		kfree(buf);

		buf = NULL;

		if (ACPI_FAILURE(status))

			return -EINVAL;

		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE);

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