[PATCH 6.18 504/552] dm-stats: fix a crash if allocation of per-cpu data fails

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mikulas Patocka <mpatocka@redhat.com>

commit cc87e26d9cce22061dc21e51e11afef29dbbc36a upstream.

If "dm_kvzalloc(percpu_alloc_size, cpu_to_node(cpu))" fails, the code
jumps to the "out" label and calls dm_stat_free. dm_stat_free does
"for_each_possible_cpu(cpu) { dm_kvfree(s->stat_percpu[cpu][0].histogram,
s->histogram_alloc_size);", which crashes with NULL pointer dereference
if s->stat_percpu[cpu] is NULL.

This commit fixes the bug by testing s->stat_percpu[cpu] for NULL before
using it.

Reported-by: Junzhe Yu <junzheyu1@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: fd2ed4d25270 ("dm: add statistics support")
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/md/dm-stats.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -178,8 +178,10 @@ static void dm_stat_free(struct rcu_head
 	kfree(s->program_id);
 	kfree(s->aux_data);
 	for_each_possible_cpu(cpu) {
-		dm_kvfree(s->stat_percpu[cpu][0].histogram, s->histogram_alloc_size);
-		dm_kvfree(s->stat_percpu[cpu], s->percpu_alloc_size);
+		if (s->stat_percpu[cpu]) {
+			dm_kvfree(s->stat_percpu[cpu][0].histogram, s->histogram_alloc_size);
+			dm_kvfree(s->stat_percpu[cpu], s->percpu_alloc_size);
+		}
 	}
 	dm_kvfree(s->stat_shared[0].tmp.histogram, s->histogram_alloc_size);
 	dm_kvfree(s, s->shared_alloc_size);