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Message-ID: <4ca63af4-df02-32e6-3531-1e5df154c13e@omp.ru>
Date: Mon, 10 Jun 2024 20:50:35 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Roman Smirnov <r.smirnov@....ru>, Jan Kara <jack@...e.com>,
<linux-kernel@...r.kernel.org>
CC: <lvc-project@...uxtesting.org>
Subject: Re: [PATCH] udf: balloc: prevent integer overflow in
udf_bitmap_free_blocks()
On 6/10/24 10:25 AM, Roman Smirnov wrote:
> An overflow may occur if the function is called with the last
> block and an offset greater than zero. It is necessary to add
> a check to avoid this.
>
> Found by Linux Verification Center (linuxtesting.org) with Svace.
>
> Signed-off-by: Roman Smirnov <r.smirnov@....ru>
> ---
> fs/udf/balloc.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/fs/udf/balloc.c b/fs/udf/balloc.c
> index ab3ffc355949..cd83bbc7d890 100644
> --- a/fs/udf/balloc.c
> +++ b/fs/udf/balloc.c
> @@ -151,6 +151,13 @@ static void udf_bitmap_free_blocks(struct super_block *sb,
> block = bloc->logicalBlockNum + offset +
> (sizeof(struct spaceBitmapDesc) << 3);
Hm, I can't say I understand this code well... Is the block variable here
counted in blocks or bytes?
>
As I've already said, we hardly need an empty line here -- just
don't add an empty line after your *if*...
> + if (block < offset + (sizeof(struct spaceBitmapDesc) << 3)) {
Thinking about this again, this addition may overflow 32 bits as well,
so it's better to compare block with bloc->logicalBlockNum...
[...]
MBR, Sergey
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