linux-kernel - Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb causes unkillable spinning

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: <alpine.LFD.0.999.0711010901290.3342@woody.linux-foundation.org>
Date:	Thu, 1 Nov 2007 09:08:45 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Nick Piggin <npiggin@...e.de>
cc:	Duane Griffin <duaneg@...da.com>,
	linux-kernel Mailing List <linux-kernel@...r.kernel.org>,
	stable@...nel.org, Hugh Dickins <hugh@...itas.com>
Subject: Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb
 causes unkillable spinning

On Thu, 1 Nov 2007, Nick Piggin wrote:
> 
> Untested patch follows

Ok, this looks ok.

Except I would remove the VM_MAYSHARE bit from the test.

That whole bit should go, in fact.

We used to make it something different: iirc, a read-only SHARED mapping 
was downgraded to a non-shared mapping, because we wanted to avoid some of 
the costs we used to have with the VM implementation (actually, I think it 
was various filesystems that don't like shared mappings because they don't 
have a per-page writeback). But we left the VM_MAYSHARE bit on, to get 
/proc/<pid>/mmap things right.

Or something like that. I forget the details. But I *think* we don't 
actually need this any more.

But basically, the "right" way to test for shared mappings is historically 
to just test the VM_MAYSHARE bit - but not *both* bits. Because VM_SHARE 
may have been artificially cleared.

Somebody should double-check my memory.

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/