* [PATCH] IB/ucma: Fix theoretical user triggered use-after-free
@ 2015-08-04 23:13 Jason Gunthorpe
[not found] ` <20150804231332.GA22959-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Jason Gunthorpe @ 2015-08-04 23:13 UTC (permalink / raw)
To: dledford-H+wXaHxf7aLQT0dZR+AlfA, Sean Hefty
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA
Something like this:
CPU A CPU B
======================== ================================
ucma_destroy_id()
wait_for_completion()
.. anything
ucma_put_ctx()
complete()
.. continues ...
ucma_leave_multicast()
mutex_lock(mut)
atomic_inc(ctx->ref)
mutex_unlock(mut)
ucma_free_ctx()
ucma_cleanup_multicast()
mutex_lock(mut)
kfree(mc)
rdma_leave_multicast(mc->ctx->cm_id,..
Fix it by latching the ref at 0. Once it goes to 0 mc and ctx cannot
leave the mutex(mut) protection.
The other atomic_inc in ucma_get_ctx is OK because mutex(mut) protects
it from racing with ucma_destroy_id.
Signed-off-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
---
drivers/infiniband/core/ucma.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 29b21213ea75..acac9eafdbf6 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -1321,10 +1321,10 @@ static ssize_t ucma_leave_multicast(struct ucma_file *file,
mc = ERR_PTR(-ENOENT);
else if (mc->ctx->file != file)
mc = ERR_PTR(-EINVAL);
- else {
+ else if (!atomic_inc_not_zero(&mc->ctx->ref))
+ mc = ERR_PTR(-ENXIO);
+ else
idr_remove(&multicast_idr, mc->id);
- atomic_inc(&mc->ctx->ref);
- }
mutex_unlock(&mut);
if (IS_ERR(mc)) {
--
1.9.1
--
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* RE: [PATCH] IB/ucma: Fix theoretical user triggered use-after-free
[not found] ` <20150804231332.GA22959-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
@ 2015-08-06 17:33 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A9023323-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
0 siblings, 1 reply; 3+ messages in thread
From: Hefty, Sean @ 2015-08-06 17:33 UTC (permalink / raw)
To: Jason Gunthorpe, dledford-H+wXaHxf7aLQT0dZR+AlfA
Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA
> Something like this:
>
> CPU A CPU B
> ======================== ================================
> ucma_destroy_id()
> wait_for_completion()
> .. anything
> ucma_put_ctx()
> complete()
> .. continues ...
> ucma_leave_multicast()
> mutex_lock(mut)
> atomic_inc(ctx->ref)
> mutex_unlock(mut)
> ucma_free_ctx()
> ucma_cleanup_multicast()
> mutex_lock(mut)
> kfree(mc)
> rdma_leave_multicast(mc->ctx->cm_id,..
>
> Fix it by latching the ref at 0. Once it goes to 0 mc and ctx cannot
> leave the mutex(mut) protection.
>
> The other atomic_inc in ucma_get_ctx is OK because mutex(mut) protects
> it from racing with ucma_destroy_id.
>
> Signed-off-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Acked-by: Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---
> drivers/infiniband/core/ucma.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/infiniband/core/ucma.c
> b/drivers/infiniband/core/ucma.c
> index 29b21213ea75..acac9eafdbf6 100644
> --- a/drivers/infiniband/core/ucma.c
> +++ b/drivers/infiniband/core/ucma.c
> @@ -1321,10 +1321,10 @@ static ssize_t ucma_leave_multicast(struct
> ucma_file *file,
> mc = ERR_PTR(-ENOENT);
> else if (mc->ctx->file != file)
> mc = ERR_PTR(-EINVAL);
> - else {
> + else if (!atomic_inc_not_zero(&mc->ctx->ref))
> + mc = ERR_PTR(-ENXIO);
> + else
> idr_remove(&multicast_idr, mc->id);
> - atomic_inc(&mc->ctx->ref);
> - }
> mutex_unlock(&mut);
>
> if (IS_ERR(mc)) {
--
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] IB/ucma: Fix theoretical user triggered use-after-free
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A9023323-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
@ 2015-08-15 1:22 ` Doug Ledford
0 siblings, 0 replies; 3+ messages in thread
From: Doug Ledford @ 2015-08-15 1:22 UTC (permalink / raw)
To: Hefty, Sean, Jason Gunthorpe; +Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA
[-- Attachment #1: Type: text/plain, Size: 1351 bytes --]
On 08/06/2015 01:33 PM, Hefty, Sean wrote:
>> Something like this:
>>
>> CPU A CPU B
>> ======================== ================================
>> ucma_destroy_id()
>> wait_for_completion()
>> .. anything
>> ucma_put_ctx()
>> complete()
>> .. continues ...
>> ucma_leave_multicast()
>> mutex_lock(mut)
>> atomic_inc(ctx->ref)
>> mutex_unlock(mut)
>> ucma_free_ctx()
>> ucma_cleanup_multicast()
>> mutex_lock(mut)
>> kfree(mc)
>> rdma_leave_multicast(mc->ctx->cm_id,..
>>
>> Fix it by latching the ref at 0. Once it goes to 0 mc and ctx cannot
>> leave the mutex(mut) protection.
>>
>> The other atomic_inc in ucma_get_ctx is OK because mutex(mut) protects
>> it from racing with ucma_destroy_id.
>>
>> Signed-off-by: Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
>
> Acked-by: Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
This has been picked up. Thanks.
--
Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
GPG KeyID: 0E572FDD
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2015-08-04 23:13 [PATCH] IB/ucma: Fix theoretical user triggered use-after-free Jason Gunthorpe
[not found] ` <20150804231332.GA22959-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-08-06 17:33 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A9023323-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-08-15 1:22 ` Doug Ledford
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