[PATCH V2] bcache:fix oops in cache_set_flush

[liequan che]

Caused by the following commit, partially revert it.

Commit 028ddcac477b ("bcache: Remove unnecessary NULL point check in
node allocations") replaced IS_ERR_OR_NULL by IS_ERR. This leads to a
NULL pointer dereference.

crash> bt
PID: 7773     TASK: ffff49cc44d69340  CPU: 57   COMMAND: "kworker/57:2"
 #0 [ffff800046373800] machine_kexec at ffffbe5039eb54a8
 #1 [ffff8000463739b0] __crash_kexec at ffffbe503a052824
 #2 [ffff8000463739e0] crash_kexec at ffffbe503a0529cc
 #3 [ffff800046373a60] die at ffffbe5039e9445c
 #4 [ffff800046373ac0] die_kernel_fault at ffffbe5039ec698c
 #5 [ffff800046373af0] __do_kernel_fault at ffffbe5039ec6a38
 #6 [ffff800046373b20] do_page_fault at ffffbe503ac76ba4
 #7 [ffff800046373b70] do_translation_fault at ffffbe503ac76ebc
 #8 [ffff800046373b90] do_mem_abort at ffffbe5039ec68ac
 #9 [ffff800046373bc0] el1_abort at ffffbe503ac669bc
crash> dis cache_set_flush+0x94
0xffffbe50121fa4c8 <cache_set_flush+148>:       str     x23, [x20, #512]

If the bcache cache disk contains damaged data,when the bcache cache
disk partition is directly operated,the system-udevd service is
triggered to call the bcache-register program to register the
bcache device, resulting in kernel oops.

This patch replaces IS_ERR() by IS_ERR_OR_NULL() to fix this.

Fixes: 028ddcac477b ("bcache: Remove unnecessary NULL point check in
node allocations")
Link: https://lore.kernel.org/all/3DF4A87A-2AC1-4893-AE5F-E921478419A9@xxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Cc: Zheng Wang <zyytlz.wz@xxxxxxx>
Cc: Coly Li <colyli@xxxxxxx>
Signed-off-by: Markus Weippert <markus@xxxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index 1f829e74db0a..e2a803683105 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1723,7 +1723,7 @@ static void cache_set_flush(struct closure *cl)
        if (!IS_ERR_OR_NULL(c->gc_thread))
                kthread_stop(c->gc_thread);

-       if (!IS_ERR_OR_NULL(c->root))
+       if (!IS_ERR(c->root))
                list_add(&c->root->list, &c->btree_cache);

        /*
--

Signed-off-by: cheliequan <cheliequan@xxxxxxxxxx>
---
 drivers/md/bcache/super.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index fd97730479d8..c72f5576e4da 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -1741,8 +1741,10 @@ static void cache_set_flush(struct closure *cl)
        if (!IS_ERR_OR_NULL(c->gc_thread))
                kthread_stop(c->gc_thread);

-       if (!IS_ERR(c->root))
-               list_add(&c->root->list, &c->btree_cache);
+       if (!IS_ERR_OR_NULL(c->root)) {
+               if (!list_empty(&c->root->list))
+                       list_add(&c->root->list, &c->btree_cache);
+       }

        /*
         * Avoid flushing cached nodes if cache set is retiring
-- 
2.33.0