Commit cb2595c1 authored by Cong Wang's avatar Cong Wang Committed by Jason Gunthorpe

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
...@@ -235,7 +235,7 @@ static struct ucma_multicast* ucma_alloc_multicast(struct ucma_context *ctx) ...@@ -235,7 +235,7 @@ static struct ucma_multicast* ucma_alloc_multicast(struct ucma_context *ctx)
return NULL; return NULL;
mutex_lock(&mut); 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); mutex_unlock(&mut);
if (mc->id < 0) if (mc->id < 0)
goto error; goto error;
...@@ -1421,6 +1421,10 @@ static ssize_t ucma_process_join(struct ucma_file *file, ...@@ -1421,6 +1421,10 @@ static ssize_t ucma_process_join(struct ucma_file *file,
goto err3; goto err3;
} }
mutex_lock(&mut);
idr_replace(&multicast_idr, mc, mc->id);
mutex_unlock(&mut);
mutex_unlock(&file->mut); mutex_unlock(&file->mut);
ucma_put_ctx(ctx); ucma_put_ctx(ctx);
return 0; return 0;
......
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