From 2949ad50711cc161721cf788711722eeeca33764 Mon Sep 17 00:00:00 2001 From: Vasiliy Kulikov Date: Sat, 19 Feb 2011 14:18:08 +0100 Subject: [PATCH] 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 Reviewed-by: WANG Cong Reviewed-by: Eugene Teo Cc: stable@kernel.org Signed-off-by: Rafael J. Wysocki --- drivers/acpi/debugfs.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/drivers/acpi/debugfs.c b/drivers/acpi/debugfs.c index 5df67f1d6c61..384f7abcff77 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); -- 2.30.2