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usb: gadget: f_fs: stricter integer overflow checks 

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: e6f3862fa1 ("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>
This commit is contained in:
Dan Carpenter 2022-09-01 17:59:42 +03:00 committed by Greg Kroah-Hartman
parent 6690986da1
commit f57004b9d9
1 changed files with 2 additions and 2 deletions
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4
drivers/usb/gadget/function/f_fs.c
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@ -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);