linux-kernel - [PATCH] kernel/resource: Fix use of ternary condition in release_mem_region

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Date:   Mon, 21 Sep 2020 23:07:48 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     david@...hat.com
Cc:     akpm@...ux-foundation.org, ardb@...nel.org, bhe@...hat.com,
        dan.j.williams@...el.com, jgg@...pe.ca, keescook@...omium.org,
        linux-acpi@...r.kernel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-nvdimm@...ts.01.org, linux-s390@...r.kernel.org,
        mhocko@...e.com, pankaj.gupta.linux@...il.com,
        richardw.yang@...ux.intel.com,
        virtualization@...ts.linux-foundation.org,
        xen-devel@...ts.xenproject.org, clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH] kernel/resource: Fix use of ternary condition in release_mem_region_adjustable

Clang warns:

kernel/resource.c:1281:53: warning: operator '?:' has lower precedence
than '|'; '|' will be evaluated first
[-Wbitwise-conditional-parentheses]
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
kernel/resource.c:1281:53: note: place parentheses around the '|'
expression to silence this warning
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                 ~~~~~~~~~~~~~~~~~~~~~~~~~ ^
kernel/resource.c:1281:53: note: place parentheses around the '?:'
expression to evaluate it first
        new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
                                                           ^
                                              (                              )
1 warning generated.

Add the parentheses as it was clearly intended for the ternary condition
to be evaluated first.

Fixes: 5fd23bd0d739 ("kernel/resource: make release_mem_region_adjustable() never fail")
Link: https://github.com/ClangBuiltLinux/linux/issues/1159
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---

Presumably, this will be squashed but I included a fixes tag
nonetheless. Apologies if this has already been noticed and fixed
already, I did not find anything on LKML.

 kernel/resource.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index ca2a666e4317..3ae2f56cc79d 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1278,7 +1278,7 @@ void release_mem_region_adjustable(resource_size_t start, resource_size_t size)
 	 * similarly).
 	 */
 retry:
-	new_res = alloc_resource(GFP_KERNEL | alloc_nofail ? __GFP_NOFAIL : 0);
+	new_res = alloc_resource(GFP_KERNEL | (alloc_nofail ? __GFP_NOFAIL : 0));
 
 	p = &parent->child;
 	write_lock(&resource_lock);

base-commit: 40ee82f47bf297e31d0c47547cd8f24ede52415a
-- 
2.28.0