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authorVasiliy Kulikov <segoon@openwall.com>2011-02-19 14:18:08 +0100
committerRafael J. Wysocki <rjw@sisk.pl>2011-02-24 19:59:06 +0100
commit2949ad50711cc161721cf788711722eeeca33764 (patch)
treeaba75138e732b43cc2c92ee2f310a0b457c70ebd
parent2aa15890f3c191326678f1bd68af61ec6b8753ec (diff)
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: 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>
-rw-r--r--drivers/acpi/debugfs.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/drivers/acpi/debugfs.c b/drivers/acpi/debugfs.c
index 5df67f1d6c6..384f7abcff7 100644
--- a/drivers/acpi/debugfs.c
+++ b/drivers/acpi/debugfs.c
@@ -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);