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, 311 insertions, 0 deletions

diff --git a/tools/include/io_uring/mini_liburing.h b/tools/include/io_uring/mini_liburing.h
new file mode 100644
index 000000000..44be4446f
--- /dev/null
+++ b/tools/include/io_uring/mini_liburing.h
@@ -0,0 +1,311 @@
+/* SPDX-License-Identifier: MIT */
+
+#include <linux/io_uring.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/uio.h>
+
+struct io_sq_ring {
+	unsigned int *head;
+	unsigned int *tail;
+	unsigned int *ring_mask;
+	unsigned int *ring_entries;
+	unsigned int *flags;
+	unsigned int *array;
+};
+
+struct io_cq_ring {
+	unsigned int *head;
+	unsigned int *tail;
+	unsigned int *ring_mask;
+	unsigned int *ring_entries;
+	struct io_uring_cqe *cqes;
+};
+
+struct io_uring_sq {
+	unsigned int *khead;
+	unsigned int *ktail;
+	unsigned int *kring_mask;
+	unsigned int *kring_entries;
+	unsigned int *kflags;
+	unsigned int *kdropped;
+	unsigned int *array;
+	struct io_uring_sqe *sqes;
+
+	unsigned int sqe_head;
+	unsigned int sqe_tail;
+
+	size_t ring_sz;
+};
+
+struct io_uring_cq {
+	unsigned int *khead;
+	unsigned int *ktail;
+	unsigned int *kring_mask;
+	unsigned int *kring_entries;
+	unsigned int *koverflow;
+	struct io_uring_cqe *cqes;
+
+	size_t ring_sz;
+};
+
+struct io_uring {
+	struct io_uring_sq sq;
+	struct io_uring_cq cq;
+	int ring_fd;
+	unsigned flags;
+};
+
+#if defined(__x86_64) || defined(__i386__)
+#define read_barrier()	__asm__ __volatile__("":::"memory")
+#define write_barrier()	__asm__ __volatile__("":::"memory")
+#else
+#define read_barrier()	__sync_synchronize()
+#define write_barrier()	__sync_synchronize()
+#endif
+
+static inline int io_uring_mmap(int fd, struct io_uring_params *p,
+				struct io_uring_sq *sq, struct io_uring_cq *cq)
+{
+	size_t size;
+	void *ptr;
+	int ret;
+
+	if (p->flags & IORING_SETUP_NO_SQARRAY) {
+		sq->ring_sz = p->cq_off.cqes;
+		sq->ring_sz += p->cq_entries * sizeof(struct io_uring_cqe);
+	} else {
+		sq->ring_sz = p->sq_off.array;
+		sq->ring_sz += p->sq_entries * sizeof(unsigned int);
+	}
+
+	ptr = mmap(0, sq->ring_sz, PROT_READ | PROT_WRITE,
+		   MAP_SHARED | MAP_POPULATE, fd, IORING_OFF_SQ_RING);
+	if (ptr == MAP_FAILED)
+		return -errno;
+	sq->khead = ptr + p->sq_off.head;
+	sq->ktail = ptr + p->sq_off.tail;
+	sq->kring_mask = ptr + p->sq_off.ring_mask;
+	sq->kring_entries = ptr + p->sq_off.ring_entries;
+	sq->kflags = ptr + p->sq_off.flags;
+	sq->kdropped = ptr + p->sq_off.dropped;
+	if (!(p->flags & IORING_SETUP_NO_SQARRAY))
+		sq->array = ptr + p->sq_off.array;
+
+	size = p->sq_entries * sizeof(struct io_uring_sqe);
+	sq->sqes = mmap(0, size, PROT_READ | PROT_WRITE,
+			MAP_SHARED | MAP_POPULATE, fd, IORING_OFF_SQES);
+	if (sq->sqes == MAP_FAILED) {
+		ret = -errno;
+err:
+		munmap(sq->khead, sq->ring_sz);
+		return ret;
+	}
+
+	cq->ring_sz = p->cq_off.cqes + p->cq_entries * sizeof(struct io_uring_cqe);
+	ptr = mmap(0, cq->ring_sz, PROT_READ | PROT_WRITE,
+		   MAP_SHARED | MAP_POPULATE, fd, IORING_OFF_CQ_RING);
+	if (ptr == MAP_FAILED) {
+		ret = -errno;
+		munmap(sq->sqes, p->sq_entries * sizeof(struct io_uring_sqe));
+		goto err;
+	}
+	cq->khead = ptr + p->cq_off.head;
+	cq->ktail = ptr + p->cq_off.tail;
+	cq->kring_mask = ptr + p->cq_off.ring_mask;
+	cq->kring_entries = ptr + p->cq_off.ring_entries;
+	cq->koverflow = ptr + p->cq_off.overflow;
+	cq->cqes = ptr + p->cq_off.cqes;
+	return 0;
+}
+
+static inline int io_uring_setup(unsigned int entries,
+				 struct io_uring_params *p)
+{
+	return syscall(__NR_io_uring_setup, entries, p);
+}
+
+static inline int io_uring_enter(int fd, unsigned int to_submit,
+				 unsigned int min_complete,
+				 unsigned int flags, sigset_t *sig)
+{
+	return syscall(__NR_io_uring_enter, fd, to_submit, min_complete,
+		       flags, sig, _NSIG / 8);
+}
+
+static inline int io_uring_queue_init_params(unsigned int entries,
+					     struct io_uring *ring,
+					     struct io_uring_params *p)
+{
+	int fd, ret;
+
+	memset(ring, 0, sizeof(*ring));
+
+	fd = io_uring_setup(entries, p);
+	if (fd < 0)
+		return fd;
+	ret = io_uring_mmap(fd, p, &ring->sq, &ring->cq);
+	if (!ret) {
+		ring->ring_fd = fd;
+		ring->flags = p->flags;
+	} else {
+		close(fd);
+	}
+	return ret;
+}
+
+static inline int io_uring_queue_init(unsigned int entries,
+				      struct io_uring *ring,
+				      unsigned int flags)
+{
+	struct io_uring_params p;
+
+	memset(&p, 0, sizeof(p));
+	p.flags = flags;
+
+	return io_uring_queue_init_params(entries, ring, &p);
+}
+
+/* Get a sqe */
+static inline struct io_uring_sqe *io_uring_get_sqe(struct io_uring *ring)
+{
+	struct io_uring_sq *sq = &ring->sq;
+
+	if (sq->sqe_tail + 1 - sq->sqe_head > *sq->kring_entries)
+		return NULL;
+	return &sq->sqes[sq->sqe_tail++ & *sq->kring_mask];
+}
+
+static inline int io_uring_wait_cqe(struct io_uring *ring,
+				    struct io_uring_cqe **cqe_ptr)
+{
+	struct io_uring_cq *cq = &ring->cq;
+	const unsigned int mask = *cq->kring_mask;
+	unsigned int head = *cq->khead;
+	int ret;
+
+	*cqe_ptr = NULL;
+	do {
+		read_barrier();
+		if (head != *cq->ktail) {
+			*cqe_ptr = &cq->cqes[head & mask];
+			break;
+		}
+		ret = io_uring_enter(ring->ring_fd, 0, 1,
+				     IORING_ENTER_GETEVENTS, NULL);
+		if (ret < 0)
+			return -errno;
+	} while (1);
+
+	return 0;
+}
+
+static inline int io_uring_submit(struct io_uring *ring)
+{
+	struct io_uring_sq *sq = &ring->sq;
+	const unsigned int mask = *sq->kring_mask;
+	unsigned int ktail, submitted, to_submit;
+	int ret;
+
+	read_barrier();
+	if (*sq->khead != *sq->ktail) {
+		submitted = *sq->kring_entries;
+		goto submit;
+	}
+	if (sq->sqe_head == sq->sqe_tail)
+		return 0;
+
+	ktail = *sq->ktail;
+	to_submit = sq->sqe_tail - sq->sqe_head;
+
+	if (!(ring->flags & IORING_SETUP_NO_SQARRAY)) {
+		for (submitted = 0; submitted < to_submit; submitted++) {
+			read_barrier();
+			sq->array[ktail++ & mask] = sq->sqe_head++ & mask;
+		}
+	} else {
+		ktail += to_submit;
+		sq->sqe_head += to_submit;
+		submitted = to_submit;
+	}
+
+	if (!submitted)
+		return 0;
+
+	if (*sq->ktail != ktail) {
+		write_barrier();
+		*sq->ktail = ktail;
+		write_barrier();
+	}
+submit:
+	ret = io_uring_enter(ring->ring_fd, submitted, 0,
+			     IORING_ENTER_GETEVENTS, NULL);
+	return ret < 0 ? -errno : ret;
+}
+
+static inline void io_uring_queue_exit(struct io_uring *ring)
+{
+	struct io_uring_sq *sq = &ring->sq;
+
+	munmap(sq->sqes, *sq->kring_entries * sizeof(struct io_uring_sqe));
+	munmap(sq->khead, sq->ring_sz);
+	close(ring->ring_fd);
+}
+
+/* Prepare and send the SQE */
+static inline void io_uring_prep_cmd(struct io_uring_sqe *sqe, int op,
+				     int sockfd,
+				     int level, int optname,
+				     const void *optval,
+				     int optlen)
+{
+	memset(sqe, 0, sizeof(*sqe));
+	sqe->opcode = (__u8)IORING_OP_URING_CMD;
+	sqe->fd = sockfd;
+	sqe->cmd_op = op;
+
+	sqe->level = level;
+	sqe->optname = optname;
+	sqe->optval = (unsigned long long)optval;
+	sqe->optlen = optlen;
+}
+
+static inline int io_uring_register_buffers(struct io_uring *ring,
+					    const struct iovec *iovecs,
+					    unsigned int nr_iovecs)
+{
+	int ret;
+
+	ret = syscall(__NR_io_uring_register, ring->ring_fd,
+		      IORING_REGISTER_BUFFERS, iovecs, nr_iovecs);
+	return (ret < 0) ? -errno : ret;
+}
+
+static inline void io_uring_prep_send(struct io_uring_sqe *sqe, int sockfd,
+				      const void *buf, size_t len, int flags)
+{
+	memset(sqe, 0, sizeof(*sqe));
+	sqe->opcode = (__u8)IORING_OP_SEND;
+	sqe->fd = sockfd;
+	sqe->addr = (unsigned long)buf;
+	sqe->len = len;
+	sqe->msg_flags = (__u32)flags;
+}
+
+static inline void io_uring_prep_sendzc(struct io_uring_sqe *sqe, int sockfd,
+					const void *buf, size_t len, int flags,
+					unsigned int zc_flags)
+{
+	io_uring_prep_send(sqe, sockfd, buf, len, flags);
+	sqe->opcode = (__u8)IORING_OP_SEND_ZC;
+	sqe->ioprio = zc_flags;
+}
+
+static inline void io_uring_cqe_seen(struct io_uring *ring)
+{
+	*(&ring->cq)->khead += 1;
+	write_barrier();
+}