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Commit 1eb9364c authored by Jason Gunthorpe's avatar Jason Gunthorpe
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IB/uverbs: Fix ordering of ucontext check in ib_uverbs_write 



During disassociation the ucontext will become NULL, however due to how
the SRCU locking works the ucontext must only be examined after looking
at the ib_dev, which governs the RCU control flow.

With the wrong ordering userspace will see EINVAL instead of EIO for a
disassociated uverbs FD, which breaks rdma-core.

Cc: stable@vger.kernel.org
Fixes: 491d5c6a ("RDMA/uverbs: Move uncontext check before SRCU read lock")
Reported-by: default avatarMark Bloch <markb@mellanox.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
Reviewed-by: default avatarLeon Romanovsky <leonro@mellanox.com>
parent 3dc7c7ba

drivers/infiniband/core/uverbs_main.c

+10 −4
Original line number Diff line number Diff line
@@ -736,10 +736,6 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf, 
	if (ret)

		return ret;



	if (!file->ucontext &&

	    (command != IB_USER_VERBS_CMD_GET_CONTEXT || extended))

		return -EINVAL;



	if (extended) {

		if (count < (sizeof(hdr) + sizeof(ex_hdr)))

			return -EINVAL;
@@ -759,6 +755,16 @@ static ssize_t ib_uverbs_write(struct file *filp, const char __user *buf, 
		goto out;

	}



	/*

	 * Must be after the ib_dev check, as once the RCU clears ib_dev ==

	 * NULL means ucontext == NULL

	 */

	if (!file->ucontext &&

	    (command != IB_USER_VERBS_CMD_GET_CONTEXT || extended)) {

		ret = -EINVAL;

		goto out;

	}



	if (!verify_command_mask(ib_dev, command, extended)) {

		ret = -EOPNOTSUPP;

		goto out;