A race condition may occur if the user calls close() on another
thread during a write() operation on the device node of the efi capsule.
This is a race condition that occurs between the efi_capsule_write()
and efi_capsule_flush() functions of efi_capsule_fops,
which ultimately results in UAF.
So, the page freeing process is modified to be done in
efi_capsule_release() instead of efi_capsule_flush().
Signed-off-by: Hyunwoo Kim <imv4bel@xxxxxxxxx>
---
drivers/firmware/efi/capsule-loader.c | 31 ++++++---------------------
1 file changed, 7 insertions(+), 24 deletions(-)
diff --git a/drivers/firmware/efi/capsule-loader.c b/drivers/firmware/efi/capsule-loader.c
index 4dde8edd53b6..cec826adcb51 100644
--- a/drivers/firmware/efi/capsule-loader.c
+++ b/drivers/firmware/efi/capsule-loader.c
@@ -242,29 +242,6 @@ static ssize_t efi_capsule_write(struct file *file, const char __user *buff,
return ret;
}
-/**
- * efi_capsule_flush - called by file close or file flush
- * @file: file pointer
- * @id: not used
- *
- * If a capsule is being partially uploaded then calling this function
- * will be treated as upload termination and will free those completed
- * buffer pages and -ECANCELED will be returned.
- **/
-static int efi_capsule_flush(struct file *file, fl_owner_t id)
-{
- int ret = 0;
- struct capsule_info *cap_info = file->private_data;
-
- if (cap_info->index > 0) {
- pr_err("capsule upload not complete\n");
- efi_free_all_buff_pages(cap_info);
- ret = -ECANCELED;
- }
-
- return ret;
-}
-
/**
* efi_capsule_release - called by file close
* @inode: not used
@@ -277,6 +254,13 @@ static int efi_capsule_release(struct inode *inode, struct file *file)
{
struct capsule_info *cap_info = file->private_data;
+ if (cap_info->index > 0 &&
+ (cap_info->header.headersize == 0 ||
+ cap_info->count < cap_info->total_size)) {
+ pr_err("capsule upload not complete\n");
+ efi_free_all_buff_pages(cap_info);
+ }
+
kfree(cap_info->pages);
kfree(cap_info->phys);
kfree(file->private_data);
@@ -324,7 +308,6 @@ static const struct file_operations efi_capsule_fops = {
.owner = THIS_MODULE,
.open = efi_capsule_open,
.write = efi_capsule_write,
- .flush = efi_capsule_flush,
.release = efi_capsule_release,
.llseek = no_llseek,
};
--
2.25.1
