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ACPI / debugfs: Fix buffer overflows, double free

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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: Vasiliy Kulikov <segoon@openwall.com>
Reviewed-by: WANG Cong <xiyou.wangcong@gmail.com>
Reviewed-by: Eugene Teo <eugeneteo@kernel.org>
Cc: stable@kernel.org
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This commit is contained in:
Vasiliy Kulikov 2011-02-19 14:18:08 +01:00 committed by Rafael J. Wysocki
parent 2aa15890f3
commit 2949ad5071
1 changed files with 14 additions and 6 deletions
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20
drivers/acpi/debugfs.c
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@ -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);