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Commit cb2595c1 authored by Cong Wang's avatar Cong Wang Committed by Jason Gunthorpe
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infiniband: fix a possible use-after-free bug 



ucma_process_join() will free the new allocated "mc" struct,
if there is any error after that, especially the copy_to_user().

But in parallel, ucma_leave_multicast() could find this "mc"
through idr_find() before ucma_process_join() frees it, since it
is already published.

So "mc" could be used in ucma_leave_multicast() after it is been
allocated and freed in ucma_process_join(), since we don't refcnt
it.

Fix this by separating "publish" from ID allocation, so that we
can get an ID first and publish it later after copy_to_user().

Fixes: c8f6a362 ("RDMA/cma: Add multicast communication support")
Reported-by: default avatarNoam Rathaus <noamr@beyondsecurity.com>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent e4b1672a

drivers/infiniband/core/ucma.c

+5 −1
Original line number Diff line number Diff line
@@ -235,7 +235,7 @@ static struct ucma_multicast* ucma_alloc_multicast(struct ucma_context *ctx) 
		return NULL;



	mutex_lock(&mut);

	mc->id = idr_alloc(&multicast_idr, mc, 0, 0, GFP_KERNEL);

	mc->id = idr_alloc(&multicast_idr, NULL, 0, 0, GFP_KERNEL);

	mutex_unlock(&mut);

	if (mc->id < 0)

		goto error;
@@ -1421,6 +1421,10 @@ static ssize_t ucma_process_join(struct ucma_file *file, 
		goto err3;

	}



	mutex_lock(&mut);

	idr_replace(&multicast_idr, mc, mc->id);

	mutex_unlock(&mut);



	mutex_unlock(&file->mut);

	ucma_put_ctx(ctx);

	return 0;