Re: [PATCH v2] fs/exfat: resolve memory leak from exfat_create_upcase_table()

From: Namjae Jeon
Date: Mon Sep 16 2024 - 07:27:38 EST


On Mon, Sep 16, 2024 at 2:21 PM Daniel Yang <danielyangkang@xxxxxxxxx> wrote:
>
> If exfat_load_upcase_table reaches end and returns -EINVAL,
> allocated memory doesn't get freed and while
> exfat_load_default_upcase_table allocates more memory, leading to a
> memory leak.
>
> Here's link to syzkaller crash report illustrating this issue:
> https://syzkaller.appspot.com/text?tag=CrashReport&x=1406c201980000
>
> Signed-off-by: Daniel Yang <danielyangkang@xxxxxxxxx>
> Reported-by: syzbot+e1c69cadec0f1a078e3d@xxxxxxxxxxxxxxxxxxxxxxxxx
> ---
> V1 -> V2: Moved the mem free to create_upcase_table
>
> fs/exfat/nls.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/exfat/nls.c b/fs/exfat/nls.c
> index afdf13c34..8828f9d29 100644
> --- a/fs/exfat/nls.c
> +++ b/fs/exfat/nls.c
> @@ -3,6 +3,7 @@
> * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
> */
>
> +#include <cerrno>
Why did you add this?

> #include <linux/string.h>
> #include <linux/slab.h>
> #include <linux/buffer_head.h>
> @@ -779,8 +780,13 @@ int exfat_create_upcase_table(struct super_block *sb)
> le32_to_cpu(ep->dentry.upcase.checksum));
>
> brelse(bh);
> - if (ret && ret != -EIO)
> + if (ret && ret != -EIO) {
> + /* free memory from exfat_load_upcase_table call */
> + if (ret == -EINVAL) {
Why did you add this check here? If you consider that ->vol_utbl is
NULL, this check is unnecessary.

Thanks.
> + exfat_free_upcase_table(sbi);
> + }
> goto load_default;
> + }
>
> /* load successfully */
> return ret;
> --
> 2.39.2
>