[PATCH 5.19 416/717] usb: gadget: f_fs: stricter integer overflow checks

Greg Kroah-Hartman
2022-10-22T08:10:25Z

From: Dan Carpenter <dan.carpenter@oracle.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@oracle.com>
Link: https://lore.kernel.org/r/YxDI3lMYomE7WCjn@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.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