linux-kernel - Re: [PATCH 1/3] uprobes: install_breakpoint() should fail if is_swbp

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: <20120601163315.GJ24279@linux.vnet.ibm.com>
Date:	Fri, 1 Jun 2012 22:03:15 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <anton@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] uprobes: install_breakpoint() should fail if
 is_swbp_insn() == T

* Oleg Nesterov <oleg@...hat.com> [2012-06-01 17:53:12]:

> On 05/31, Oleg Nesterov wrote:
> >
> > __find_next_vma_info() checks tmpvi->mm == vma->vm_mm to detect the
> > already visited mm/vma. However, afaics this can be false positive?
> 
> Yes, but I guess this is harmless, we can rely on uprobe_mmap.
> 
> 
> 
> But. Doesn't this mean we can greatly simplify register_for_each_vma()
> and make it O(n) ?
> 
> Unless I missed something, we can simply create the list of
> mm/vaddr structures under ->i_mmap_mutex (vma_prio_tree_foreach), then
> register_for_each_vma() can process the list and that is all.


If I remember correctly, we cannot allocate the list elements under
i_mmap_mutex. We dont know how many list elements to allocate.

This is what Peter had to say : https://lkml.org/lkml/2011/6/27/72

"Because we try to take i_mmap_mutex during reclaim, trying to unmap
pages. So suppose we do an allocation while holding i_mmap_mutex, find
there's no free memory, try and unmap a page in order to free it, and
we're stuck."

> 
> If another mapping comes after we drop i_mmap_mutex, uprobe_mmap()
> should be called and it should install the bp.
> 

-- 
Thanks and Regards
Srikar

--
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/