linux-kernel - Re: [PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build breakage

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Message-ID: <aRI-ohUyQLxIY1vu@smile.fi.intel.com>
Date: Mon, 10 Nov 2025 21:36:02 +0200
From: "andriy.shevchenko@...ux.intel.com" <andriy.shevchenko@...ux.intel.com>
To: Viacheslav Dubeyko <Slava.Dubeyko@....com>
Cc: "ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>,
	"llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nathan@...nel.org" <nathan@...nel.org>,
	"justinstitt@...gle.com" <justinstitt@...gle.com>,
	"idryomov@...il.com" <idryomov@...il.com>,
	Xiubo Li <xiubli@...hat.com>,
	"nick.desaulniers+lkml@...il.com" <nick.desaulniers+lkml@...il.com>,
	"morbo@...gle.com" <morbo@...gle.com>
Subject: Re: [PATCH v1 1/1] libceph: Amend checking to fix `make W=1` build
 breakage

On Mon, Nov 10, 2025 at 07:28:36PM +0000, Viacheslav Dubeyko wrote:
> On Mon, 2025-11-10 at 15:46 +0100, Andy Shevchenko wrote:

...

> >  	ceph_decode_32_safe(p, end, len, e_inval);
> >  	if (len == 0 && incremental)
> >  		return NULL;	/* new_pg_temp: [] to remove */
> > -	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> > +	if ((size_t)len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
> >  		return ERR_PTR(-EINVAL);
> >  
> >  	ceph_decode_need(p, end, len * sizeof(u32), e_inval);

> I am guessing... What if we change the declaration of len on size_t, then could
> it be more clear solution here? For example, let's consider this for both cases:
> 
> size_t len, i;
> 
> Could it eliminate the issue and to make the Clang happy? Or could it introduce
> another warnings/issues?

Probably, but the code is pierced with the sizeof(u32) and alike, moreover
size_t is architecture-dependent type, while the set of macros in decode.h
seems to operate on the fixed-width type. That said, I prefer my way of fixing
this. But if you find another, better one, I am all ears!

*Also note, I'm not familiar with the guts of the ceph, so maybe your solution
is the best, but I want more people to confirm this.

-- 
With Best Regards,
Andy Shevchenko