thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 116 insertions, 0 deletions

diff --git a/include/uapi/rdma/ionic-abi.h b/include/uapi/rdma/ionic-abi.h
new file mode 100644
index 000000000..2c70ac149
--- /dev/null
+++ b/include/uapi/rdma/ionic-abi.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (C) 2018-2025, Advanced Micro Devices, Inc */
+
+#ifndef IONIC_ABI_H
+#define IONIC_ABI_H
+
+#include <linux/types.h>
+
+#define IONIC_ABI_VERSION	1
+
+#define IONIC_EXPDB_64		1
+#define IONIC_EXPDB_128		2
+#define IONIC_EXPDB_256		4
+#define IONIC_EXPDB_512		8
+
+#define IONIC_EXPDB_SQ		1
+#define IONIC_EXPDB_RQ		2
+
+#define IONIC_CMB_ENABLE	1
+#define IONIC_CMB_REQUIRE	2
+#define IONIC_CMB_EXPDB		4
+#define IONIC_CMB_WC		8
+#define IONIC_CMB_UC		16
+
+struct ionic_ctx_req {
+	__u32 rsvd[2];
+};
+
+struct ionic_ctx_resp {
+	__u32 rsvd;
+	__u32 page_shift;
+
+	__aligned_u64 dbell_offset;
+
+	__u16 version;
+	__u8 qp_opcodes;
+	__u8 admin_opcodes;
+
+	__u8 sq_qtype;
+	__u8 rq_qtype;
+	__u8 cq_qtype;
+	__u8 admin_qtype;
+
+	__u8 max_stride;
+	__u8 max_spec;
+	__u8 udma_count;
+	__u8 expdb_mask;
+	__u8 expdb_qtypes;
+
+	__u8 rsvd2[3];
+	__aligned_u64 phc_offset;
+};
+
+struct ionic_qdesc {
+	__aligned_u64 addr;
+	__u32 size;
+	__u16 mask;
+	__u8 depth_log2;
+	__u8 stride_log2;
+};
+
+struct ionic_ah_resp {
+	__u32 ahid;
+	__u32 pad;
+};
+
+struct ionic_cq_req {
+	struct ionic_qdesc cq[2];
+	__u8 udma_mask;
+	__u8 rsvd[7];
+};
+
+struct ionic_cq_resp {
+	__u32 cqid[2];
+	__u8 udma_mask;
+	__u8 rsvd[7];
+};
+
+struct ionic_qp_req {
+	struct ionic_qdesc sq;
+	struct ionic_qdesc rq;
+	__u8 sq_spec;
+	__u8 rq_spec;
+	__u8 sq_cmb;
+	__u8 rq_cmb;
+	__u8 udma_mask;
+	__u8 rsvd[3];
+};
+
+struct ionic_qp_resp {
+	__u32 qpid;
+	__u8 sq_cmb;
+	__u8 rq_cmb;
+	__u8 udma_idx;
+	__u8 rsvd[1];
+	__aligned_u64 sq_cmb_offset;
+	__aligned_u64 rq_cmb_offset;
+};
+
+struct ionic_srq_req {
+	struct ionic_qdesc rq;
+	__u8 rq_spec;
+	__u8 rq_cmb;
+	__u8 udma_mask;
+	__u8 rsvd[5];
+};
+
+struct ionic_srq_resp {
+	__u32 qpid;
+	__u8 rq_cmb;
+	__u8 udma_idx;
+	__u8 rsvd[2];
+	__aligned_u64 rq_cmb_offset;
+};
+
+#endif /* IONIC_ABI_H */