ibcore: Fix a use-after-free in ucma_resolve_ip().
There is a race condition between ucma_close() and ucma_resolve_ip(): CPU0 CPU1 ucma_resolve_ip(): ucma_close(): ctx = ucma_get_ctx(file, cmd.id); list_for_each_entry_safe(ctx, tmp, &file->ctx_list, list) { mutex_lock(&mut); idr_remove(&ctx_idr, ctx->id); mutex_unlock(&mut); ... mutex_lock(&mut); if (!ctx->closing) { mutex_unlock(&mut); rdma_destroy_id(ctx->cm_id); ... ucma_free_ctx(ctx); } ret = rdma_resolve_addr(); ucma_put_ctx(ctx); Before idr_remove(), ucma_get_ctx() could still find the ctx and after rdma_destroy_id(), rdma_resolve_addr() may still access id_priv pointer. Also, ucma_put_ctx() may use ctx after ucma_free_ctx() too. ucma_close() should call ucma_put_ctx() too which tests the refcnt and waits for the last one releasing it. The similar pattern is already used by ucma_destroy_id(). Linux commit: 5fe23f262e0548ca7f19fb79f89059a60d087d22 MFC after: 1 week Reviewed by: kib Sponsored by: Mellanox Technologies // NVIDIA Networking
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@ -1705,6 +1705,8 @@ static int ucma_close(struct inode *inode, struct file *filp)
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mutex_lock(&mut);
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if (!ctx->closing) {
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mutex_unlock(&mut);
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ucma_put_ctx(ctx);
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wait_for_completion(&ctx->comp);
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/* rdma_destroy_id ensures that no event handlers are
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* inflight for that id before releasing it.
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*/
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