Re: [PATCH 4.14 22/86] null_blk: Always check queue mode setting from configfs

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

On Mon, May 29, 2023 at 10:16:36PM +0530, Harshit Mogalapalli wrote:
> Hi Greg,
> 
> On 29/05/23 12:39 am, Greg Kroah-Hartman wrote:
> > From: Chaitanya Kulkarni <kch@nvidia.com>
> > 
> > [ Upstream commit 63f8793ee60513a09f110ea460a6ff2c33811cdb ]
> > 
> > Make sure to check device queue mode in the null_validate_conf() and
> > return error for NULL_Q_RQ as we don't allow legacy I/O path, without
> > this patch we get OOPs when queue mode is set to 1 from configfs,
> > following are repro steps :-
> > 
> > modprobe null_blk nr_devices=0
> > mkdir config/nullb/nullb0
> > echo 1 > config/nullb/nullb0/memory_backed
> > echo 4096 > config/nullb/nullb0/blocksize
> > echo 20480 > config/nullb/nullb0/size
> > echo 1 > config/nullb/nullb0/queue_mode
> > echo 1 > config/nullb/nullb0/power
> > 
> > Entering kdb (current=0xffff88810acdd080, pid 2372) on processor 42 Oops: (null)
> > due to oops @ 0xffffffffc041c329
> > CPU: 42 PID: 2372 Comm: sh Tainted: G           O     N 6.3.0-rc5lblk+ #5
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
> > RIP: 0010:null_add_dev.part.0+0xd9/0x720 [null_blk]
> > Code: 01 00 00 85 d2 0f 85 a1 03 00 00 48 83 bb 08 01 00 00 00 0f 85 f7 03 00 00 80 bb 62 01 00 00 00 48 8b 75 20 0f 85 6d 02 00 00 <48> 89 6e 60 48 8b 75 20 bf 06 00 00 00 e8 f5 37 2c c1 48 8b 75 20
> > RSP: 0018:ffffc900052cbde0 EFLAGS: 00010246
> > RAX: 0000000000000001 RBX: ffff88811084d800 RCX: 0000000000000001
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888100042e00
> > RBP: ffff8881053d8200 R08: ffffc900052cbd68 R09: ffff888105db2000
> > R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000002
> > R13: ffff888104765200 R14: ffff88810eec1748 R15: ffff88810eec1740
> > FS:  00007fd445fd1740(0000) GS:ffff8897dfc80000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000000000060 CR3: 0000000166a00000 CR4: 0000000000350ee0
> > DR0: ffffffff8437a488 DR1: ffffffff8437a489 DR2: ffffffff8437a48a
> > DR3: ffffffff8437a48b DR6: 00000000ffff0ff0 DR7: 0000000000000400
> > Call Trace:
> >   <TASK>
> >   nullb_device_power_store+0xd1/0x120 [null_blk]
> >   configfs_write_iter+0xb4/0x120
> >   vfs_write+0x2ba/0x3c0
> >   ksys_write+0x5f/0xe0
> >   do_syscall_64+0x3b/0x90
> >   entry_SYSCALL_64_after_hwframe+0x72/0xdc
> > RIP: 0033:0x7fd4460c57a7
> > Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
> > RSP: 002b:00007ffd3792a4a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007fd4460c57a7
> > RDX: 0000000000000002 RSI: 000055b43c02e4c0 RDI: 0000000000000001
> > RBP: 000055b43c02e4c0 R08: 000000000000000a R09: 00007fd44615b4e0
> > R10: 00007fd44615b3e0 R11: 0000000000000246 R12: 0000000000000002
> > R13: 00007fd446198520 R14: 0000000000000002 R15: 00007fd446198700
> >   </TASK>
> > 
> > Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
> > Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
> > Reviewed-by: Ming Lei <ming.lei@redhat.com>
> > Reviewed-by: Nitesh Shetty <nj.shetty@samsung.com>
> > Link: https://lore.kernel.org/r/20230416220339.43845-1-kch@nvidia.com
> > Signed-off-by: Jens Axboe <axboe@kernel.dk>
> > Signed-off-by: Sasha Levin <sashal@kernel.org>
> > ---
> >   drivers/block/null_blk.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
> > index b499e72b2847e..38660b5cfb73c 100644
> > --- a/drivers/block/null_blk.c
> > +++ b/drivers/block/null_blk.c
> > @@ -1780,6 +1780,11 @@ static int null_init_tag_set(struct nullb *nullb, struct blk_mq_tag_set *set)
> >   static void null_validate_conf(struct nullb_device *dev)
> >   {
> > +	if (dev->queue_mode == NULL_Q_RQ) {
> > +		pr_err("legacy IO path is no longer available\n");
> > +		return -EINVAL;
> > +	}
> > +
> 
> This patch introduces a warning during build:
> 
>  drivers/block/null_blk.c: In function 'null_validate_conf':
>  drivers/block/null_blk.c:1785:10: warning: 'return' with a value, in
> function returning void
>     return -EINVAL;
>            ^
>  drivers/block/null_blk.c:1781:13: note: declared here
>   static void null_validate_conf(struct nullb_device *dev)
>               ^~~~~~~~~~~~~~~~~~
> 
> 
> The commit message explains on how to reproduce the bug, with my
> CONFIG(CONFIG_BLK_DEV_NULL_BLK enabled) I am unable to reproduce this bug on
> 4.14.315. So I think we can drop this patch from 4.14.y release as it
> introduces the above warning.
> 
> Commit 5c4bd1f40c23d is not present on 4.14.y, which changes the return type
> of this.
> 
> Given that the bug mentioned in the commit message is not reproducible on
> 4.14.y, I think we can drop this patch instead of taking a
> prerequisite(5c4bd1f40c23d).
> 
> Note: I don't see this patch being queued up for 5.4.y.
> 
> [Thanks to Vegard for helping with this.]

Thanks, I've dropped it now!

greg k-h