linux-kernel - [PATCH v2] IB/rdmavt: Fix variable shadowing issue in rvt_create

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Date:   Tue,  9 Jul 2019 16:05:53 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>
Cc:     Kamenee Arumugam <kamenee.arumugam@...el.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH v2] IB/rdmavt: Fix variable shadowing issue in rvt_create_cq

clang warns:

drivers/infiniband/sw/rdmavt/cq.c:260:7: warning: variable 'err' is used
uninitialized whenever 'if' condition is true
[-Wsometimes-uninitialized]
                if (err)
                    ^~~
drivers/infiniband/sw/rdmavt/cq.c:310:9: note: uninitialized use occurs
here
        return err;
               ^~~
drivers/infiniband/sw/rdmavt/cq.c:260:3: note: remove the 'if' if its
condition is always false
                if (err)
                ^~~~~~~~
drivers/infiniband/sw/rdmavt/cq.c:253:7: warning: variable 'err' is used
uninitialized whenever 'if' condition is true
[-Wsometimes-uninitialized]
                if (!cq->ip) {
                    ^~~~~~~
drivers/infiniband/sw/rdmavt/cq.c:310:9: note: uninitialized use occurs
here
        return err;
               ^~~
drivers/infiniband/sw/rdmavt/cq.c:253:3: note: remove the 'if' if its
condition is always false
                if (!cq->ip) {
                ^~~~~~~~~~~~~~
drivers/infiniband/sw/rdmavt/cq.c:211:9: note: initialize the variable
'err' to silence this warning
        int err;
               ^
                = 0
2 warnings generated.

The function scoped err variable is uninitialized when the flow jumps
into the if statement. The if scoped err variable shadows the function
scoped err variable, preventing the err assignments within the if
statement to be reflected at the function level, which will cause
uninitialized use when the goto statements are taken.

Just remove the if scoped err declaration so that there is only one
copy of the err variable for this function.

Fixes: 239b0e52d8aa ("IB/hfi1: Move rvt_cq_wc struct into uapi directory")
Link: https://github.com/ClangBuiltLinux/linux/issues/594
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---

v1 -> v2:

* Updated the wording of the commit message to use proper terms like
  scoping and shadowing, thanks to review from Nick (let me know if the
  wording isn't up to snuff).

 drivers/infiniband/sw/rdmavt/cq.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/infiniband/sw/rdmavt/cq.c b/drivers/infiniband/sw/rdmavt/cq.c
index fac87b13329d..a85571a4cf57 100644
--- a/drivers/infiniband/sw/rdmavt/cq.c
+++ b/drivers/infiniband/sw/rdmavt/cq.c
@@ -247,8 +247,6 @@ int rvt_create_cq(struct ib_cq *ibcq, const struct ib_cq_init_attr *attr,
 	 * See rvt_mmap() for details.
 	 */
 	if (udata && udata->outlen >= sizeof(__u64)) {
-		int err;
-
 		cq->ip = rvt_create_mmap_info(rdi, sz, udata, u_wc);
 		if (!cq->ip) {
 			err = -ENOMEM;
-- 
2.22.0