linux-kernel - Re: [PATCH] ligtnvm: fix double blk_put

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Message-ID: <520b34ab-6fa9-6c85-1f45-28c1b71fef30@lightnvm.io>
Date:   Thu, 20 Apr 2017 15:46:42 +0200
From:   Matias Bjørling <mb@...htnvm.io>
To:     Rakesh Pandit <rakesh@...era.com>
Cc:     Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ligtnvm: fix double blk_put_queue on same queue

On 04/19/2017 11:47 PM, Rakesh Pandit wrote:
> On an error path in NVM_DEV_CREATE ioctl blk_put_queue is being called
> twice: one via blk_cleanup_queue and another via put_disk.  Straight fix
> seems to remove queue pointer so that disk_release never ends up caling
> blk_put_queue again.
>
>   [  391.808827] WARNING: CPU: 1 PID: 1250 at lib/refcount.c:128 refcount_sub_and_test+0x70/0x80
>   [  391.808830] refcount_t: underflow; use-after-free.
>   [ 391.808832] Modules linked in: nf_conntrack_netbios_ns............
>   [  391.809052] CPU: 1 PID: 1250 Comm: nvme Not tainted.........
>   [  391.809057] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
>              BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
>   [  391.809060] Call Trace:
>   [  391.809079]  dump_stack+0x63/0x86
>   [  391.809094]  __warn+0xcb/0xf0
>   [  391.809103]  warn_slowpath_fmt+0x5f/0x80
>   [  391.809118]  refcount_sub_and_test+0x70/0x80
>   [  391.809125]  refcount_dec_and_test+0x11/0x20
>   [  391.809136]  kobject_put+0x1f/0x60
>   [  391.809149]  blk_put_queue+0x15/0x20
>   [  391.809159]  disk_release+0xae/0xf0
>   [  391.809172]  device_release+0x32/0x90
>   [  391.809184]  kobject_release+0x6a/0x170
>   [  391.809196]  kobject_put+0x2f/0x60
>   [  391.809206]  put_disk+0x17/0x20
>   [  391.809219]  nvm_ioctl_dev_create.isra.16+0x897/0xa30
>   [  391.809236]  nvm_ctl_ioctl+0x23c/0x4c0
>   [  391.809248]  do_vfs_ioctl+0xa3/0x5f0
>   [  391.809258]  SyS_ioctl+0x79/0x90
>   [  391.809271]  entry_SYSCALL_64_fastpath+0x1a/0xa9
>   [  391.809280] RIP: 0033:0x7f5d3ef363c7
>   [  391.809286] RSP: 002b:00007ffc72ed8d78 EFLAGS: 00000206 ORIG_RAX: 0000000000000010
>   [  391.809296] RAX: ffffffffffffffda RBX: 00007ffc72edb552 RCX: 00007f5d3ef363c7
>   [  391.809301] RDX: 00007ffc72ed8d90 RSI: 0000000040804c22 RDI: 0000000000000003
>   [  391.809306] RBP: 0000000000000001 R08: 0000000000000020 R09: 0000000000000001
>   [  391.809311] R10: 000000000000053f R11: 0000000000000206 R12: 0000000000000000
>   [  391.809316] R13: 0000000000000000 R14: 00007ffc72edb58d R15: 00007ffc72edb581
>
> Signed-off-by: Rakesh Pandit <rakesh@...era.com>
> ---
>  drivers/lightnvm/core.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
> index 2c26af3..5d7aa45 100644
> --- a/drivers/lightnvm/core.c
> +++ b/drivers/lightnvm/core.c
> @@ -309,6 +309,7 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create)
>  		tt->exit(targetdata);
>  err_init:
>  	blk_cleanup_queue(tqueue);
> +	tdisk->queue = NULL;
>  err_disk:
>  	put_disk(tdisk);
>  err_dev:
>

Thanks Rakesh. Jens, is this too late for -rc1? :)

Reviewed-by: Matias Bjørling <matias@...xlabs.com>