Re: [PATCH 3/9] VFS: Introduce a mount context
From: Julia Lawall
Date: Thu May 04 2017 - 02:29:44 EST
On Wed, 3 May 2017, Joe Perches wrote:
> (adding Julia Lawall and cocci)
> On Wed, 2017-05-03 at 13:38 -0700, Matthew Wilcox wrote:
> > On Wed, May 03, 2017 at 11:26:38AM -0700, Joe Perches wrote:
> > > On Wed, 2017-05-03 at 14:13 -0400, Jeff Layton wrote:
> > > > On Wed, 2017-05-03 at 17:04 +0100, David Howells wrote:
> > > > > + oo = kmalloc((opts->num_mnt_opts + 1) * sizeof(char *),
> > > > > + GFP_KERNEL);
> > If we're picking nits, then this should be kcalloc in case somebody
> > passed in 2^31 in num_mnt_opts.
> There are likely dozens to hundreds of possible/silent
> multiplication overflow defects in the kernel, not just
> in allocations.
> Auditing the sources would seem labor intensive.
> Perhaps coccinelle could help find them.
> Perhaps there should be some overflow checking functions
> added to math64.h
> Maybe some form like:
> u32 u32_mul_u32_u32(u32 a, u32 b)
> u32 res = a * b;
> WARN_ON(a != 0 && res / a != b);
> return res;
Coccinelle doesn't kow about the values of variables. It would need some
heuristics about where potentially large values can come from.