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Subject[PATCH 4.19 57/81] mm/vmpressure.c: fix a signedness bug in vmpressure_register_event()
Date
From: Dan Carpenter <dan.carpenter@oracle.com>

commit 518a86713078168acd67cf50bc0b45d54b4cce6c upstream.

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.

[akpm@linux-foundation.org: reduce implicit and explicit typecasting]
[akpm@linux-foundation.org: fix return value, add comment, per Matthew]
Link: http://lkml.kernel.org/r/20190925110449.GO3264@mwanda
Fixes: 3cadfa2b9497 ("mm/vmpressure.c: convert to use match_string() helper")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: David Rientjes <rientjes@google.com>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Enrico Weigelt <info@metux.net>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
mm/vmpressure.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)

--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -358,6 +358,9 @@ void vmpressure_prio(gfp_t gfp, struct m
* "hierarchy" or "local").
*
* To be used as memcg event method.
+ *
+ * Return: 0 on success, -ENOMEM on memory failure or -EINVAL if @args could
+ * not be parsed.
*/
int vmpressure_register_event(struct mem_cgroup *memcg,
struct eventfd_ctx *eventfd, const char *args)
@@ -365,7 +368,7 @@ int vmpressure_register_event(struct mem
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;
@@ -378,20 +381,18 @@ int vmpressure_register_event(struct mem

/* Find required level */
token = strsep(&spec, ",");
- level = match_string(vmpressure_str_levels, VMPRESSURE_NUM_LEVELS, token);
- if (level < 0) {
- ret = level;
+ ret = match_string(vmpressure_str_levels, VMPRESSURE_NUM_LEVELS, token);
+ if (ret < 0)
goto out;
- }
+ level = ret;

/* Find optional mode */
token = strsep(&spec, ",");
if (token) {
- mode = match_string(vmpressure_str_modes, VMPRESSURE_NUM_MODES, token);
- if (mode < 0) {
- ret = mode;
+ ret = match_string(vmpressure_str_modes, VMPRESSURE_NUM_MODES, token);
+ if (ret < 0)
goto out;
- }
+ mode = ret;
}

ev = kzalloc(sizeof(*ev), GFP_KERNEL);
@@ -407,6 +408,7 @@ int vmpressure_register_event(struct mem
mutex_lock(&vmpr->events_lock);
list_add(&ev->node, &vmpr->events);
mutex_unlock(&vmpr->events_lock);
+ ret = 0;
out:
kfree(spec_orig);
return ret;

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