From 1eb9364ce81d9445ad6f9d44921a91d2a6597156 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe Date: Tue, 12 Jun 2018 09:40:23 -0600 Subject: [PATCH] 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: 491d5c6a3023 ("RDMA/uverbs: Move uncontext check before SRCU read lock") Reported-by: Mark Bloch Signed-off-by: Jason Gunthorpe Reviewed-by: Leon Romanovsky --- drivers/infiniband/core/uverbs_main.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c index 3ae2339dd27a..2094d136513d 100644 --- a/drivers/infiniband/core/uverbs_main.c +++ b/drivers/infiniband/core/uverbs_main.c @@ -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; -- 2.30.2