linux-kernel - Re: [PATCH] mm: vmalloc: Prevent use after free in _vm_unmap

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]

Date:   Wed, 24 Mar 2021 08:59:37 +0530
From:   Vijayanand Jitta <vjitta@...eaurora.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, vinmenon@...eaurora.org
Subject: Re: [PATCH] mm: vmalloc: Prevent use after free in _vm_unmap_aliases



On 3/18/2021 10:29 PM, Uladzislau Rezki wrote:
> On Thu, Mar 18, 2021 at 03:38:25PM +0530, vjitta@...eaurora.org wrote:
>> From: Vijayanand Jitta <vjitta@...eaurora.org>
>>
>> A potential use after free can occur in _vm_unmap_aliases
>> where an already freed vmap_area could be accessed, Consider
>> the following scenario:
>>
>> Process 1						Process 2
>>
>> __vm_unmap_aliases					__vm_unmap_aliases
>> 	purge_fragmented_blocks_allcpus				rcu_read_lock()
>> 		rcu_read_lock()
>> 			list_del_rcu(&vb->free_list)
>> 									list_for_each_entry_rcu(vb .. )
>> 	__purge_vmap_area_lazy
>> 		kmem_cache_free(va)
>> 										va_start = vb->va->va_start
> Or maybe we should switch to kfree_rcu() instead of kmem_cache_free()?
> 
> --
> Vlad Rezki
> 

Thanks for suggestion.

I see free_vmap_area_lock (spinlock) is taken in __purge_vmap_area_lazy
while it loops through list and calls kmem_cache_free on va's. So, looks
like we can't replace it with kfree_rcu as it might cause scheduling
within atomic context.

Thanks,
Vijay
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of Code Aurora Forum, hosted by The Linux Foundation