linux-kernel - [PATCH 6.0 512/862] usb: gadget: f_fs: stricter integer overflow checks

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Message-Id: <20221019083312.610349805@linuxfoundation.org>
Date:   Wed, 19 Oct 2022 10:29:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 6.0 512/862] usb: gadget: f_fs: stricter integer overflow checks

From: Dan Carpenter <dan.carpenter@...cle.com>

[ Upstream commit f57004b9d96755cd6a243b51c267be4016b4563c ]

This from static analysis.  The vla_item() takes a size and adds it to
the total.  It has a built in integer overflow check so if it encounters
an integer overflow anywhere then it records the total as SIZE_MAX.

However there is an issue here because the "lang_count*(needed_count+1)"
multiplication can overflow.  Technically the "lang_count + 1" addition
could overflow too, but that would be detected and is harmless.  Fix
both using the new size_add() and size_mul() functions.

Fixes: e6f3862fa1ec ("usb: gadget: FunctionFS: Remove VLAIS usage from gadget code")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
Link: https://lore.kernel.org/r/YxDI3lMYomE7WCjn@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/usb/gadget/function/f_fs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index e0fa4b186ec6..36184a762527 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2645,10 +2645,10 @@ static int __ffs_data_got_strings(struct ffs_data *ffs,
 		unsigned i = 0;
 		vla_group(d);
 		vla_item(d, struct usb_gadget_strings *, stringtabs,
-			lang_count + 1);
+			size_add(lang_count, 1));
 		vla_item(d, struct usb_gadget_strings, stringtab, lang_count);
 		vla_item(d, struct usb_string, strings,
-			lang_count*(needed_count+1));
+			size_mul(lang_count, (needed_count + 1)));
 
 		char *vlabuf = kmalloc(vla_group_size(d), GFP_KERNEL);
 
-- 
2.35.1