From d3aa3e060c4a80827eb801fc448debc9daa7c46b Mon Sep 17 00:00:00 2001
From: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Date: Thu, 16 Mar 2023 14:55:06 +0800
Subject: [PATCH] dm stats: check for and propagate alloc_percpu failure
Git-commit: d3aa3e060c4a80827eb801fc448debc9daa7c46b
Patch-mainline: v6.3-rc4
References: git-fixes

Check alloc_precpu()'s return value and return an error from
dm_stats_init() if it fails. Update alloc_dev() to fail if
dm_stats_init() does.

Otherwise, a NULL pointer dereference will occur in dm_stats_cleanup()
even if dm-stats isn't being actively used.

(Coly Li: refreshed for Linux 4.12 based SUSE kernel)

Fixes: fd2ed4d25270 ("dm: add statistics support")
Cc: stable@vger.kernel.org
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Coly Li <colyli@suse.de>

---
 drivers/md/dm-stats.c |    7 ++++++-
 drivers/md/dm-stats.h |    2 +-
 drivers/md/dm.c       |    4 +++-
 3 files changed, 10 insertions(+), 3 deletions(-)

--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -187,7 +187,7 @@ static int dm_stat_in_flight(struct dm_s
 	       atomic_read(&shared->in_flight[WRITE]);
 }
 
-void dm_stats_init(struct dm_stats *stats)
+int dm_stats_init(struct dm_stats *stats)
 {
 	int cpu;
 	struct dm_stats_last_position *last;
@@ -195,11 +195,16 @@ void dm_stats_init(struct dm_stats *stat
 	mutex_init(&stats->mutex);
 	INIT_LIST_HEAD(&stats->list);
 	stats->last = alloc_percpu(struct dm_stats_last_position);
+	if (!stats->last)
+		return -ENOMEM;
+
 	for_each_possible_cpu(cpu) {
 		last = per_cpu_ptr(stats->last, cpu);
 		last->last_sector = (sector_t)ULLONG_MAX;
 		last->last_rw = UINT_MAX;
 	}
+
+	return 0;
 }
 
 void dm_stats_cleanup(struct dm_stats *stats)
--- a/drivers/md/dm-stats.h
+++ b/drivers/md/dm-stats.h
@@ -21,7 +21,7 @@ struct dm_stats_aux {
 	unsigned long long duration_ns;
 };
 
-void dm_stats_init(struct dm_stats *st);
+int dm_stats_init(struct dm_stats *st);
 void dm_stats_cleanup(struct dm_stats *st);
 
 struct mapped_device;
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1978,7 +1978,9 @@ static struct mapped_device *alloc_dev(i
 	bio_set_dev(&md->flush_bio, md->bdev);
 	md->flush_bio.bi_opf = REQ_OP_WRITE | REQ_PREFLUSH | REQ_SYNC;
 
-	dm_stats_init(&md->stats);
+	r = dm_stats_init(&md->stats);
+	if (r < 0)
+		goto bad;
 
 	/* Populate the mapping, nobody knows we exist yet */
 	spin_lock(&_minor_lock);