[PATCH 4.14 061/125] md/raid5: fix oops during stripe resizing

Greg Kroah-Hartman
2020-11-03T21:12:57Z

From: Song Liu <songliubraving@fb.com>

commit b44c018cdf748b96b676ba09fdbc5b34fc443ada upstream.

KoWei reported crash during raid5 reshape:

[ 1032.252932] Oops: 0002 [#1] SMP PTI
[...]
[ 1032.252943] RIP: 0010:memcpy_erms+0x6/0x10
[...]
[ 1032.252947] RSP: 0018:ffffba1ac0c03b78 EFLAGS: 00010286
[ 1032.252949] RAX: 0000784ac0000000 RBX: ffff91bec3d09740 RCX: 0000000000001000
[ 1032.252951] RDX: 0000000000001000 RSI: ffff91be6781c000 RDI: 0000784ac0000000
[ 1032.252953] RBP: ffffba1ac0c03bd8 R08: 0000000000001000 R09: ffffba1ac0c03bf8
[ 1032.252954] R10: 0000000000000000 R11: 0000000000000000 R12: ffffba1ac0c03bf8
[ 1032.252955] R13: 0000000000001000 R14: 0000000000000000 R15: 0000000000000000
[ 1032.252958] FS: 0000000000000000(0000) GS:ffff91becf500000(0000) knlGS:0000000000000000
[ 1032.252959] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1032.252961] CR2: 0000784ac0000000 CR3: 000000031780a002 CR4: 00000000001606e0
[ 1032.252962] Call Trace:
[ 1032.252969] ? async_memcpy+0x179/0x1000 [async_memcpy]
[ 1032.252977] ? raid5_release_stripe+0x8e/0x110 [raid456]
[ 1032.252982] handle_stripe_expansion+0x15a/0x1f0 [raid456]
[ 1032.252988] handle_stripe+0x592/0x1270 [raid456]
[ 1032.252993] handle_active_stripes.isra.0+0x3cb/0x5a0 [raid456]
[ 1032.252999] raid5d+0x35c/0x550 [raid456]
[ 1032.253002] ? schedule+0x42/0xb0
[ 1032.253006] ? schedule_timeout+0x10e/0x160
[ 1032.253011] md_thread+0x97/0x160
[ 1032.253015] ? wait_woken+0x80/0x80
[ 1032.253019] kthread+0x104/0x140
[ 1032.253022] ? md_start_sync+0x60/0x60
[ 1032.253024] ? kthread_park+0x90/0x90
[ 1032.253027] ret_from_fork+0x35/0x40

This is because cache_size_mutex was unlocked too early in resize_stripes,
which races with grow_one_stripe() that grow_one_stripe() allocates a
stripe with wrong pool_size.

Fix this issue by unlocking cache_size_mutex after updating pool_size.

Cc: <stable@vger.kernel.org> # v4.4+
Reported-by: KoWei Sung <winders@amazon.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/raid5.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -2415,8 +2415,6 @@ static int resize_stripes(struct r5conf
} else
err = -ENOMEM;

- mutex_unlock(&conf->cache_size_mutex);
-
conf->slab_cache = sc;
conf->active_name = 1-conf->active_name;

@@ -2439,6 +2437,8 @@ static int resize_stripes(struct r5conf

if (!err)
conf->pool_size = newsize;
+ mutex_unlock(&conf->cache_size_mutex);
+
return err;
}