linux-kernel - Re: [PATCH] slab: remove __alloc_size attribute from __kmalloc_track

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Message-ID: <YhCZ5m+uw/xqS9W2@kroah.com>
Date:   Sat, 19 Feb 2022 08:19:02 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Daniel Micay <danielmicay@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>, linux-mm@...ck.org,
        llvm@...ts.linux.dev
Subject: Re: [PATCH] slab: remove __alloc_size attribute from
 __kmalloc_track_caller

On Fri, Feb 18, 2022 at 07:54:14PM +0100, Vlastimil Babka wrote:
> On 2/18/22 18:57, Greg Kroah-Hartman wrote:
> > On Fri, Feb 18, 2022 at 06:14:55PM +0100, Vlastimil Babka wrote:
> >> On 2/18/22 14:13, Greg Kroah-Hartman wrote:
> >> > Commit c37495d6254c ("slab: add __alloc_size attributes for better
> >> > bounds checking") added __alloc_size attributes to a bunch of kmalloc
> >> > function prototypes.  Unfortunately the change to __kmalloc_track_caller
> >> > seems to cause clang to generate broken code and the first time this is
> >> > called when booting, the box will crash.
> >> > 
> >> > While the compiler problems are being reworked and attempted to be
> >> > solved, let's just drop the attribute to solve the issue now.  Once it
> >> > is resolved it can be added back.
> >> 
> >> Could we instead wrap it in some #ifdef that' only true for clang build?
> >> That would make the workaround more precise and self-documented. Even
> >> better if it can trigger using clang version range and once a fixed
> >> clang version is here, it can be updated to stay true for older clangs.
> > 
> > It's not doing all that much good like this, let's just remove it for
> > now until it does actually provide a benifit and not just crash the box :)
> > 
> > This is only 1 function, that is used in only a very small number of
> > callers.  I do not think it will be missed.
> 
> Fair enough, added to the slab tree:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git/log/?h=for-5.17/fixup5
> 

Thanks!