linux-kernel - [PATCH] mm, vmpressure: Fix a signedness bug in vmpressure_register

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Date:   Wed, 25 Sep 2019 14:04:49 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     tglx@...utronix.de, Enrico Weigelt <info@...ux.net>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] mm, vmpressure: Fix a signedness bug in
 vmpressure_register_event()

The "mode" and "level" variables are enums and in this context GCC will
treat them as unsigned ints so the error handling is never triggered.

I also removed the bogus initializer because it isn't required any more
and it's sort of confusing.

Fixes: 3cadfa2b9497 ("mm/vmpressure.c: convert to use match_string() helper")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 mm/vmpressure.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index f3b50811497a..fe077500cf20 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -362,7 +362,7 @@ int vmpressure_register_event(struct mem_cgroup *memcg,
 	struct vmpressure *vmpr = memcg_to_vmpressure(memcg);
 	struct vmpressure_event *ev;
 	enum vmpressure_modes mode = VMPRESSURE_NO_PASSTHROUGH;
-	enum vmpressure_levels level = -1;
+	enum vmpressure_levels level;
 	char *spec, *spec_orig;
 	char *token;
 	int ret = 0;
@@ -376,7 +376,7 @@ int vmpressure_register_event(struct mem_cgroup *memcg,
 	/* Find required level */
 	token = strsep(&spec, ",");
 	level = match_string(vmpressure_str_levels, VMPRESSURE_NUM_LEVELS, token);
-	if (level < 0) {
+	if ((int)level < 0) {
 		ret = level;
 		goto out;
 	}
@@ -385,7 +385,7 @@ int vmpressure_register_event(struct mem_cgroup *memcg,
 	token = strsep(&spec, ",");
 	if (token) {
 		mode = match_string(vmpressure_str_modes, VMPRESSURE_NUM_MODES, token);
-		if (mode < 0) {
+		if ((int)mode < 0) {
 			ret = mode;
 			goto out;
 		}
-- 
2.20.1