From: Linus Torvalds <torvalds@osdl.org>
To: Rajesh Venkatasubramanian <vrajesh@umich.edu>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, Linux-MM@kvack.org
Subject: Re: [PATCH] mremap NULL pointer dereference fix
Date: Mon, 16 Feb 2004 21:38:26 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.58.0402162127220.30742@home.osdl.org> (raw)
In-Reply-To: <Pine.SOL.4.44.0402162331580.20215-100000@blue.engin.umich.edu>
On Mon, 16 Feb 2004, Rajesh Venkatasubramanian wrote:
>
> This path fixes a NULL pointer dereference bug in mremap. In
> move_one_page we need to re-check the src because an allocation
> for the dst page table can drop page_table_lock, and somebody
> else can invalidate the src.
Ugly, but yes. The "!page_table_present(mm, new_addr))" code just before
the "alloc_one_pte_map()" should already have done this, but while the
page tables themselves are safe due to us holding the mm semaphore, the
pte entry itself at "src" is not.
I hate that code, and your patch makes it even uglier. This code could do
with a real clean-up, but for now I think your patch will do.
Thanks,
Linus
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next prev parent reply other threads:[~2004-02-17 5:38 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-17 4:41 Rajesh Venkatasubramanian
2004-02-17 5:31 ` Andrew Morton
2004-02-17 5:38 ` Linus Torvalds [this message]
2004-02-17 5:49 ` Linus Torvalds
2004-02-17 6:00 ` Andrew Morton
2004-02-17 6:06 ` Linus Torvalds
2004-02-17 13:23 ` Rajesh Venkatasubramanian
2004-02-17 21:33 ` Rajesh Venkatasubramanian
2004-02-19 14:29 ` [PATCH] orphaned ptes -- mremap vs. truncate race Rajesh Venkatasubramanian
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