linux-kernel - Re: [PATCH v7 6/7] mseal, system mappings: uprobe mapping

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <qhdax7njcpjfprjmp6l5nhg2ach4qzbhfevviw6fbevnsdwflf@7sauzehmu74t>
Date: Wed, 26 Feb 2025 13:19:18 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Oleg Nesterov <oleg@...hat.com>, jeffxu@...omium.org,
        akpm@...ux-foundation.org, keescook@...omium.org, jannh@...gle.com,
        torvalds@...ux-foundation.org, vbabka@...e.cz,
        adhemerval.zanella@...aro.org, avagin@...il.com,
        benjamin@...solutions.net, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-mm@...ck.org,
        jorgelo@...omium.org, sroettger@...gle.com, hch@....de,
        ojeda@...nel.org, thomas.weissschuh@...utronix.de, adobriyan@...il.com,
        johannes@...solutions.net, pedro.falcato@...il.com, hca@...ux.ibm.com,
        willy@...radead.org, anna-maria@...utronix.de, mark.rutland@....com,
        linus.walleij@...aro.org, Jason@...c4.com, deller@....de,
        rdunlap@...radead.org, davem@...emloft.net, peterx@...hat.com,
        f.fainelli@...il.com, gerg@...nel.org, dave.hansen@...ux.intel.com,
        mingo@...nel.org, ardb@...nel.org, mhocko@...e.com,
        42.hyeyoo@...il.com, peterz@...radead.org, ardb@...gle.com,
        enh@...gle.com, rientjes@...gle.com, groeck@...omium.org,
        mpe@...erman.id.au, aleksandr.mikhalitsyn@...onical.com,
        mike.rapoport@...il.com
Subject: Re: [PATCH v7 6/7] mseal, system mappings: uprobe mapping

* Lorenzo Stoakes <lorenzo.stoakes@...cle.com> [250226 13:06]:
> On Wed, Feb 26, 2025 at 07:01:36PM +0100, Oleg Nesterov wrote:
> > On 02/26, Lorenzo Stoakes wrote:
> > >
> > > On Wed, Feb 26, 2025 at 05:26:04PM +0100, Oleg Nesterov wrote:
> > > > On 02/24, jeffxu@...omium.org wrote:
> > > > >
> > > > > Unlike other system mappings, the uprobe mapping is not
> > > > > established during program startup. However, its lifetime is the same
> > > > > as the process's lifetime. It could be sealed from creation.
> > > >
> > > > Agreed, VM_SEALED should be always for the "[uprobes]" vma, regardless
> > > > of config options.
> > >
> > > If you think this ought to be the case generally, then perhaps we should
> > > drop this patch from the commit and just do this separately as a
> > > permanent-on thing, if you are sure this is fine + want it?
> >
> > See below...
> >
> > > An aside - we _definitely_ cannot allow this -system mapping stuff- to be
> > > enabled without a config option,
> >
> > This is clear.
> >
> > But as for uprobes in particular I do think that VM_SEALED is always fine.
> >
> > Do we really want it? I dunno. If a task unmaps its "[uprobes]" vma it
> > will crash when it hits the uprobes bp next time. Unless the probed insn
> > can be emulated and it is not ret-probe. Do we really care? Again, I don't
> > know.
> >
> > Should this change come as a separate patch? I don't understand why it should
> > but I am fine either way.
> >
> > In short. please do what you think is right,  VM_SEALED can't hurt uprobes ;)
> >
> > > > 	#ifdef CONFIG_64BIT
> > > > 	/* VM is sealed, in vm_flags */
> > > > 	#define VM_SEALED	_BITUL(63)
> > > > +	#else
> > > > +	#define VM_SEALED	0

nit, we have VM_NONE for this (it's also 0, so no real difference)

> > > > 	#endif
> > >
> > > This has been raised a few times. Jeff objects to this
> >
> > OK,
> >
> > > > and then simply
> > > >
> > > > 	vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
> > > > -				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO,
> > > > +				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO|VM_SEALED,
> > > >
> > > > ?
> > >
> > > Nah you'd have to do:
> > >
> > >
> > > > 	vma = _install_special_mapping(mm, area->vaddr, PAGE_SIZE,
> > > 				VM_EXEC|VM_MAYEXEC|VM_DONTCOPY|VM_IO
> > > #ifdef CONFIG_64BIT
> > > 				VM_SEALED
> > > #endif
> > > 				,
> >
> > Why??? With the proposed change above VM_SEALED == 0 if !CONFIG_64BIT.
> >
> 
> Like I said, Jeff opposes the change. I disagree with him, and agree with you,
> because this is very silly.

Discussion here [1].

> 
> But I don't want to hold up this series with that discussion (this is for his
> sake...)
> 
> > Oleg.
> >
> 
> Jeff - perhaps drop this and let's return to it in a follow up so this series
> isn't held up?
> 

...

Thanks,
Liam

[1]. https://lore.kernel.org/all/CABi2SkVKhjShryG0K-NSjjBvGs0UOVsY-6MQVOuQCkfuph5K8Q@mail.gmail.com/