On Tue, Jul 9, 2019 at 3:13 PM Nathan Chancellor
<natechancellor@xxxxxxxxx> wrote:
>
> clang warns:
>
> drivers/infiniband/sw/rdmavt/cq.c:260:7: warning: variable 'err' is used
Oh, !$*@, this is a tricky one. While the if scoped `err` declared on
L250 is initialized when used at L260, the function scoped `err`
declared on L211 is not initialized when it is used on L310 when
control flow enters the if on L249 then the goto on L255 or L261. So
this is a bug due to the if scoped `err` "shadowing" the function
scoped `err`.
Maybe not important enough to send a v2, but I feel like the commit
message should say something along the lines of `fix a potential use
of uninitialized memory due to shadowing`. Either way, this fixes a
real bug, so thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> 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.
>
> There are two err declarations in this function: at the top and within
> an if statement; clang warns because the assignments to err in the if
> statement are local to the if statement so err will be used
> uninitialized if this error handling is used. Remove the if statement's
> err declaration so that everything works properly.
>
> Fixes: 239b0e52d8aa ("IB/hfi1: Move rvt_cq_wc struct into uapi directory")
> Link: https://github.com/ClangBuiltLinux/linux/issues/594
> Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> ---
> 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;
> -
--
Thanks,
~Nick Desaulniers
