From: Hyunwoo Kim <imv4bel@xxxxxxxxx> commit 9cb636b5f6a8cc6d1b50809ec8f8d33ae0c84c95 upstream. 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@xxxxxxxxxxxxxxx> # v4.9+ Signed-off-by: Hyunwoo Kim <imv4bel@xxxxxxxxx> Link: https://lore.kernel.org/all/20220907102920.GA88602@ubuntu/ Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/firmware/efi/capsule-loader.c | 31 +++++++------------------------ 1 file changed, 7 insertions(+), 24 deletions(-) --- a/drivers/firmware/efi/capsule-loader.c +++ b/drivers/firmware/efi/capsule-loader.c @@ -242,29 +242,6 @@ failed: } /** - * 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 * @file: file pointer @@ -276,6 +253,13 @@ static int efi_capsule_release(struct in { 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); @@ -323,7 +307,6 @@ static const struct file_operations efi_ .owner = THIS_MODULE, .open = efi_capsule_open, .write = efi_capsule_write, - .flush = efi_capsule_flush, .release = efi_capsule_release, .llseek = no_llseek, };
