The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

9cb636b5f6a8 ("efi: capsule-loader: Fix use-after-free in efi_capsule_write") 5dce14b9d1a2 ("efi/capsule: Clean up pr_err/_info() messages")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 9cb636b5f6a8cc6d1b50809ec8f8d33ae0c84c95 Mon Sep 17 00:00:00 2001 From: Hyunwoo Kim imv4bel@gmail.com Date: Wed, 7 Sep 2022 09:07:14 -0700 Subject: [PATCH] efi: capsule-loader: Fix use-after-free in efi_capsule_write

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().

Cc: stable@vger.kernel.org # v4.9+ Signed-off-by: Hyunwoo Kim imv4bel@gmail.com Link: https://lore.kernel.org/all/20220907102920.GA88602@ubuntu/ Signed-off-by: Ard Biesheuvel ardb@kernel.org

diff --git a/drivers/firmware/efi/capsule-loader.c b/drivers/firmware/efi/capsule-loader.c index 4dde8edd53b6..3e8d4b51a814 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, };