* [PATCH] Export mm_update_next_owner function for unuse_mm.
@ 2018-12-18 3:42 gchen.guomin
2018-12-18 4:38 ` Michael S. Tsirkin
2018-12-18 12:47 ` Matthew Wilcox
0 siblings, 2 replies; 3+ messages in thread
From: gchen.guomin @ 2018-12-18 3:42 UTC (permalink / raw)
To: Michael S. Tsirkin, Jason Wang, Christoph Hellwig, Andrew Morton,
Luis R. Rodriguez, guominchen
Cc: guomin chen, Eric W. Biederman, Dominik Brodowski, Arnd Bergmann,
linux-kernel, linux-mm
From: guomin chen <gchen.guomin@gmail.com>
When mm->owner is modified by exit_mm, if the new owner directly calls
unuse_mm to exit, it will cause Use-After-Free. Due to the unuse_mm()
directly sets tsk->mm=NULL.
Under normal circumstances,When do_exit exits, mm->owner will
be updated on exit_mm(). but when the kernel process calls
unuse_mm() and then exits,mm->owner cannot be updated. And it
will point to a task that has been released.
The current issue flow is as follows:
Process C Process A Process B
qemu-system-x86_64: kernel:vhost_net kernel: vhost_net
open /dev/vhost-net
VHOST_SET_OWNER create kthread vhost-%d create kthread vhost-%d
network init use_mm() use_mm()
... ...
Abnormal exited
...
do_exit
exit_mm()
update mm->owner to A
exit_files()
close_files()
kthread_should_stop() unuse_mm()
Stop Process A tsk->mm=NULL
do_exit()
can't update owner
A exit completed vhost-%d rcv first package
vhost-%d build rcv buffer for vq
page fault
access mm & mm->owner
NOW,mm->owner still pointer A
kernel UAF
stop Process B
Although I am having this issue on vhost_net,But it affects all users of
unuse_mm.
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: guomin chen <gchen.guomin@gmail.com>
---
kernel/exit.c | 1 +
mm/mmu_context.c | 1 +
2 files changed, 2 insertions(+)
diff --git a/kernel/exit.c b/kernel/exit.c
index 0e21e6d..9e046dd 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -486,6 +486,7 @@ void mm_update_next_owner(struct mm_struct *mm)
task_unlock(c);
put_task_struct(c);
}
+EXPORT_SYMBOL(mm_update_next_owner);
#endif /* CONFIG_MEMCG */
/*
diff --git a/mm/mmu_context.c b/mm/mmu_context.c
index 3e612ae..9eb81aa 100644
--- a/mm/mmu_context.c
+++ b/mm/mmu_context.c
@@ -60,5 +60,6 @@ void unuse_mm(struct mm_struct *mm)
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
task_unlock(tsk);
+ mm_update_next_owner(mm);
}
EXPORT_SYMBOL_GPL(unuse_mm);
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] Export mm_update_next_owner function for unuse_mm.
2018-12-18 3:42 [PATCH] Export mm_update_next_owner function for unuse_mm gchen.guomin
@ 2018-12-18 4:38 ` Michael S. Tsirkin
2018-12-18 12:47 ` Matthew Wilcox
1 sibling, 0 replies; 3+ messages in thread
From: Michael S. Tsirkin @ 2018-12-18 4:38 UTC (permalink / raw)
To: gchen.guomin
Cc: Jason Wang, Christoph Hellwig, Andrew Morton, Luis R. Rodriguez,
guominchen, Eric W. Biederman, Dominik Brodowski, Arnd Bergmann,
linux-kernel, linux-mm
On Tue, Dec 18, 2018 at 11:42:11AM +0800, gchen.guomin@gmail.com wrote:
> From: guomin chen <gchen.guomin@gmail.com>
>
> When mm->owner is modified by exit_mm, if the new owner directly calls
> unuse_mm to exit, it will cause Use-After-Free. Due to the unuse_mm()
> directly sets tsk->mm=NULL.
>
> Under normal circumstances,When do_exit exits, mm->owner will
> be updated on exit_mm(). but when the kernel process calls
> unuse_mm() and then exits,mm->owner cannot be updated. And it
> will point to a task that has been released.
>
> The current issue flow is as follows:
> Process C Process A Process B
> qemu-system-x86_64: kernel:vhost_net kernel: vhost_net
> open /dev/vhost-net
> VHOST_SET_OWNER create kthread vhost-%d create kthread vhost-%d
> network init use_mm() use_mm()
> ... ...
> Abnormal exited
> ...
> do_exit
> exit_mm()
> update mm->owner to A
> exit_files()
> close_files()
> kthread_should_stop() unuse_mm()
> Stop Process A tsk->mm=NULL
> do_exit()
> can't update owner
> A exit completed vhost-%d rcv first package
> vhost-%d build rcv buffer for vq
> page fault
> access mm & mm->owner
> NOW,mm->owner still pointer A
> kernel UAF
> stop Process B
>
> Although I am having this issue on vhost_net,But it affects all users of
> unuse_mm.
>
> Cc: "Eric W. Biederman" <ebiederm@xmission.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: "Luis R. Rodriguez" <mcgrof@kernel.org>
> Cc: Dominik Brodowski <linux@dominikbrodowski.net>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Christoph Hellwig <hch@infradead.org>
> Signed-off-by: guomin chen <gchen.guomin@gmail.com>
> ---
> kernel/exit.c | 1 +
> mm/mmu_context.c | 1 +
> 2 files changed, 2 insertions(+)
>
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 0e21e6d..9e046dd 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -486,6 +486,7 @@ void mm_update_next_owner(struct mm_struct *mm)
> task_unlock(c);
> put_task_struct(c);
> }
> +EXPORT_SYMBOL(mm_update_next_owner);
> #endif /* CONFIG_MEMCG */
>
> /*
So why export it? Is that still needed?
> diff --git a/mm/mmu_context.c b/mm/mmu_context.c
> index 3e612ae..9eb81aa 100644
> --- a/mm/mmu_context.c
> +++ b/mm/mmu_context.c
> @@ -60,5 +60,6 @@ void unuse_mm(struct mm_struct *mm)
> /* active_mm is still 'mm' */
> enter_lazy_tlb(mm, tsk);
> task_unlock(tsk);
> + mm_update_next_owner(mm);
> }
> EXPORT_SYMBOL_GPL(unuse_mm);
> --
> 1.8.3.1
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Export mm_update_next_owner function for unuse_mm.
2018-12-18 3:42 [PATCH] Export mm_update_next_owner function for unuse_mm gchen.guomin
2018-12-18 4:38 ` Michael S. Tsirkin
@ 2018-12-18 12:47 ` Matthew Wilcox
1 sibling, 0 replies; 3+ messages in thread
From: Matthew Wilcox @ 2018-12-18 12:47 UTC (permalink / raw)
To: gchen.guomin
Cc: Michael S. Tsirkin, Jason Wang, Christoph Hellwig, Andrew Morton,
Luis R. Rodriguez, guominchen, Eric W. Biederman,
Dominik Brodowski, Arnd Bergmann, linux-kernel, linux-mm
On Tue, Dec 18, 2018 at 11:42:11AM +0800, gchen.guomin@gmail.com wrote:
> +EXPORT_SYMBOL(mm_update_next_owner);
Unless you've figured out how to build mmu_context.c as a module, you
don't need to EXPORT the symbol. Just the below hunk is enough.
> diff --git a/mm/mmu_context.c b/mm/mmu_context.c
> index 3e612ae..9eb81aa 100644
> --- a/mm/mmu_context.c
> +++ b/mm/mmu_context.c
> @@ -60,5 +60,6 @@ void unuse_mm(struct mm_struct *mm)
> /* active_mm is still 'mm' */
> enter_lazy_tlb(mm, tsk);
> task_unlock(tsk);
> + mm_update_next_owner(mm);
> }
> EXPORT_SYMBOL_GPL(unuse_mm);
> --
> 1.8.3.1
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-12-18 3:42 [PATCH] Export mm_update_next_owner function for unuse_mm gchen.guomin
2018-12-18 4:38 ` Michael S. Tsirkin
2018-12-18 12:47 ` Matthew Wilcox
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