Re: [PATCH] md/raid5: init batch_xxx for new sh at resize_stripes

From: NeilBrown
Date: Mon May 04 2015 - 03:24:50 EST

On Mon, 4 May 2015 13:50:24 +0800 Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
wrote:

> This is to fix a kernel NULL dereference oops introduced by commit
> 59fc630b("RAID5: batch adjacent full stripe write"), which introduced
> several batch_xxx fields, and did initiation for them at grow_one_stripes(),
> but forgot to do same at resize_stripes().
>
> This oops can be easily triggered by following steps:
>
> __create RAID5 /dev/md0
> __grow /dev/md0
> mdadm --wait /dev/md0
> dd if=/dev/zero of=/dev/md0
>
> Here is the detailed oops log:
>
> [ 32.384499] BUG: unable to handle kernel NULL pointer dereference at (null)
> [ 32.385366] IP: [<ffffffff81844082>] add_stripe_bio+0x48d/0x544
> [ 32.385955] PGD 373f3067 PUD 36e34067 PMD 0
> [ 32.386404] Oops: 0002 [#1] SMP
> [ 32.386740] Modules linked in:
> [ 32.387040] CPU: 0 PID: 1059 Comm: kworker/u2:2 Not tainted 4.0.0-next-20150427+ #107
> [ 32.387762] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
> [ 32.388044] Workqueue: writeback bdi_writeback_workfn (flush-9:0)
> [ 32.388044] task: ffff88003d038000 ti: ffff88003d40c000 task.ti: ffff88003d40c000
> [ 32.388044] RIP: 0010:[<ffffffff81844082>] [<ffffffff81844082>] add_stripe_bio+0x48d/0x544
> [ 32.388044] RSP: 0000:ffff88003d40f6f8 EFLAGS: 00010046
> [ 32.388044] RAX: 0000000000000000 RBX: ffff880037168cd0 RCX: ffff880037179a28
> [ 32.388044] RDX: ffff880037168d58 RSI: 0000000000000000 RDI: ffff880037179a20
> [ 32.388044] RBP: ffff88003d40f738 R08: 0000000000000410 R09: 0000000000000410
> [ 32.388044] R10: 0000000000000410 R11: 0000000000000002 R12: ffff8800371799a0
> [ 32.388044] R13: ffff88003c3d0800 R14: 0000000000000001 R15: ffff880037179a08
> [ 32.388044] FS: 0000000000000000(0000) GS:ffff88003fc00000(0000) knlGS:0000000000000000
> [ 32.388044] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [ 32.388044] CR2: 0000000000000000 CR3: 0000000036e33000 CR4: 00000000000006f0
> [ 32.388044] Stack:
> [ 32.388044] 0000000200000000 ffff880037168d38 ffff88003d40f738 ffff88003c3abd00
> [ 32.388044] ffff88003c2df800 ffff88003c3d0800 0000000000000408 ffff88003c3d0b54
> [ 32.388044] ffff88003d40f828 ffffffff8184b9ea ffffffff3d40f7e8 0000000000000292
> [ 32.388044] Call Trace:
> [ 32.388044] [<ffffffff8184b9ea>] make_request+0x7a8/0xaee
> [ 32.388044] [<ffffffff81120387>] ? wait_woken+0x79/0x79
> [ 32.388044] [<ffffffff811e9a85>] ? kmem_cache_alloc+0x95/0x1b6
> [ 32.388044] [<ffffffff8186b944>] md_make_request+0xeb/0x1c3
> [ 32.388044] [<ffffffff811a3025>] ? mempool_alloc+0x64/0x127
> [ 32.388044] [<ffffffff81481575>] generic_make_request+0x9c/0xdb
> [ 32.388044] [<ffffffff814816aa>] submit_bio+0xf6/0x134
> [ 32.388044] [<ffffffff8122a1f7>] _submit_bh+0x119/0x141
> [ 32.388044] [<ffffffff8122a22f>] submit_bh+0x10/0x12
> [ 32.388044] [<ffffffff8122bbb9>] __block_write_full_page.constprop.30+0x1a3/0x2a4
> [ 32.388044] [<ffffffff8122bead>] ? I_BDEV+0xd/0xd
> [ 32.388044] [<ffffffff8122bd65>] block_write_full_page+0xab/0xaf
> [ 32.388044] [<ffffffff8122c657>] blkdev_writepage+0x18/0x1a
> [ 32.388044] [<ffffffff811a9853>] __writepage+0x14/0x2d
> [ 32.388044] [<ffffffff811a9ef3>] write_cache_pages+0x29a/0x3a7
> [ 32.388044] [<ffffffff811a983f>] ? mapping_tagged+0x14/0x14
> [ 32.388044] [<ffffffff811aa03e>] generic_writepages+0x3e/0x56
> [ 32.388044] [<ffffffff811ab638>] do_writepages+0x1e/0x2c
> [ 32.388044] [<ffffffff812229ed>] __writeback_single_inode+0x5b/0x27e
> [ 32.388044] [<ffffffff81222ec7>] writeback_sb_inodes+0x1dc/0x358
> [ 32.388044] [<ffffffff812230c2>] __writeback_inodes_wb+0x7f/0xb8
> [ 32.388044] [<ffffffff812232b9>] wb_writeback+0x11a/0x271
> [ 32.388044] [<ffffffff811aa483>] ? global_dirty_limits+0x1b/0xfd
> [ 32.388044] [<ffffffff8122399c>] bdi_writeback_workfn+0x1ae/0x360
> [ 32.388044] [<ffffffff81101bab>] process_one_work+0x1c2/0x340
> [ 32.388044] [<ffffffff81102571>] worker_thread+0x28b/0x389
> [ 32.388044] [<ffffffff811022e6>] ? cancel_delayed_work_sync+0x15/0x15
> [ 32.388044] [<ffffffff81106936>] kthread+0xd2/0xda
> [ 32.388044] [<ffffffff81106864>] ? kthread_create_on_node+0x17c/0x17c
> [ 32.388044] [<ffffffff81a16682>] ret_from_fork+0x42/0x70
> [ 32.388044] [<ffffffff81106864>] ? kthread_create_on_node+0x17c/0x17c
> [ 32.388044] Code: 84 24 90 00 00 00 48 8d 93 88 00 00 00 49 8d 8c 24 88 00 00 00 49 89 94 24 90 00 00 00 48 89 8b 88 00 00 00 48 89 83 90 00 00 00 <48> 89 10 66 41 83 84 24 80 00 00 00 01 3e 0f ba 73 48 06 72 02
> [ 32.388044] RIP [<ffffffff81844082>] add_stripe_bio+0x48d/0x544
> [ 32.388044] RSP <ffff88003d40f6f8>
> [ 32.388044] CR2: 0000000000000000
> [ 32.388044] ---[ end trace 2b255d3f55be9eb3 ]---
>
> Cc: Shaohua Li <shli@xxxxxxxxxx>
> Signed-off-by: Yuanhan Liu <yuanhan.liu@xxxxxxxxxxxxxxx>
> ---
> drivers/md/raid5.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index 697d77a..7b074f7 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -2217,6 +2217,10 @@ static int resize_stripes(struct r5conf *conf, int newsize)
> if (!p)
> err = -ENOMEM;
> }
> +
> + spin_lock_init(&nsh->batch_lock);
> + INIT_LIST_HEAD(&nsh->batch_list);
> + nsh->batch_head = NULL;
> release_stripe(nsh);
> }
> /* critical section pass, GFP_NOIO no longer needed */

Thanks!

However I already have the following fix queued - though not pushed out
you. I probably would have got it into -rc2 except that I was chasing
another raid5 bug. The
BUG_ON(sh->batch_head);

in handle_stripe_fill() fires when I run the mdadm selftests. I got caught
up chasing that and didn't push the other fix.

Thanks,
NeilBrown


From 3dd8ba734349e602fe17d647ce3da5f4a13748aa Mon Sep 17 00:00:00 2001
From: NeilBrown <neilb@xxxxxxx>
Date: Thu, 30 Apr 2015 11:24:28 +1000
Subject: [PATCH] md/raid5 new alloc_stripe function.


diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 77dfd720aaa0..91a1e8b26b52 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -1971,17 +1971,30 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
put_cpu();
}

+static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp)
+{
+ struct stripe_head *sh;
+
+ sh = kmem_cache_zalloc(sc, gfp);
+ if (sh) {
+ spin_lock_init(&sh->stripe_lock);
+ spin_lock_init(&sh->batch_lock);
+ INIT_LIST_HEAD(&sh->batch_list);
+ INIT_LIST_HEAD(&sh->lru);
+ atomic_set(&sh->count, 1);
+ }
+ return sh;
+}
static int grow_one_stripe(struct r5conf *conf, gfp_t gfp)
{
struct stripe_head *sh;
- sh = kmem_cache_zalloc(conf->slab_cache, gfp);
+
+ sh = alloc_stripe(conf->slab_cache, gfp);
if (!sh)
return 0;

sh->raid_conf = conf;

- spin_lock_init(&sh->stripe_lock);
-
if (grow_buffers(sh, gfp)) {
shrink_buffers(sh);
kmem_cache_free(conf->slab_cache, sh);
@@ -1990,13 +2003,8 @@ static int grow_one_stripe(struct r5conf *conf, gfp_t gfp)
sh->hash_lock_index =
conf->max_nr_stripes % NR_STRIPE_HASH_LOCKS;
/* we just created an active stripe so... */
- atomic_set(&sh->count, 1);
atomic_inc(&conf->active_stripes);
- INIT_LIST_HEAD(&sh->lru);

- spin_lock_init(&sh->batch_lock);
- INIT_LIST_HEAD(&sh->batch_list);
- sh->batch_head = NULL;
release_stripe(sh);
conf->max_nr_stripes++;
return 1;
@@ -2109,13 +2117,11 @@ static int resize_stripes(struct r5conf *conf, int newsize)
return -ENOMEM;

for (i = conf->max_nr_stripes; i; i--) {
- nsh = kmem_cache_zalloc(sc, GFP_KERNEL);
+ nsh = alloc_stripe(sc, GFP_KERNEL);
if (!nsh)
break;

nsh->raid_conf = conf;
- spin_lock_init(&nsh->stripe_lock);
-
list_add(&nsh->lru, &newstripes);
}
if (i) {
@@ -2142,13 +2148,11 @@ static int resize_stripes(struct r5conf *conf, int newsize)
lock_device_hash_lock(conf, hash));
osh = get_free_stripe(conf, hash);
unlock_device_hash_lock(conf, hash);
- atomic_set(&nsh->count, 1);
+
for(i=0; i<conf->pool_size; i++) {
nsh->dev[i].page = osh->dev[i].page;
nsh->dev[i].orig_page = osh->dev[i].page;
}
- for( ; i<newsize; i++)
- nsh->dev[i].page = NULL;
nsh->hash_lock_index = hash;
kmem_cache_free(conf->slab_cache, osh);
cnt++;

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