netdev - Re: [RFC] Make find_tcp

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] [day] [month] [year] [list]

Message-ID: <l3abhimtyv24oogb5l2is7hml6fcs6vlthbd7n4rmnyou24e5l@capndvics4kt>
Date: Tue, 14 May 2024 18:12:26 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        netdev@...r.kernel.org, Arjun Roy <arjunroy@...gle.com>
Subject: Re: [RFC] Make find_tcp_vma() more efficient

* Suren Baghdasaryan <surenb@...gle.com> [240503 18:29]:
> On Fri, Apr 26, 2024 at 10:15 AM Matthew Wilcox <willy@...radead.org> wrote:
> >
> > Liam asked me if we could do away with the "bool *mmap_locked"
> > parameter, and the problem is that some architctures don't support
> > CONFIG_PER_VMA_LOCK yet.  But we can abstract it ... something like this
> > maybe?
> >
> > (not particularly proposing this for inclusion; just wrote it and want
> > to get it out of my tree so I can get back to other projects.  If anyone
> > wants it, they can test it and submit it for inclusion and stick my
> > S-o-B on it)
> 
> I went through all uses of vma_end_read() to convince myself this is
> safe with CONFIG_PER_VMA_LOCK=n and the change seems fine from
> correctness POV. However the fact that in this configuration
> lock_vma_under_mmap_lock()==NOP and vma_end_read()==mmap_read_unlock()
> does not feel right to me. Current code is more explicit about which
> lock is held and I think it's easier to understand.
> A new interface like below might be a bit better but I'm not sure if
> it's worth it:
> 
...

We could do something like we do in the release_fault_lock(), but
without using the FAULT flag..

/* Naming is hard. */
static inline void release_vma_modification_lock(
		struct vm_area_struct *vma)
{                                                                                                                                      
#ifdef CONFIG_PER_VMA_LOCK
        if (rwsem_is_locked(&vma->vm_lock->lock))
                vma_end_read(vma);                                                                                                
        else                                                                                                                           
                mmap_read_unlock(vma->vm_mm);                                                                                     
#else
        mmap_read_unlock(vma->vm_mm);                                                                                     
#endif
}