netdev - Re: [PATCH mlx5-next 1/7] RDMA/mlx5: Don't set esc

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Message-ID: <20211012140433.GV2744544@nvidia.com>
Date:   Tue, 12 Oct 2021 11:04:33 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Aharon Landau <aharonl@...dia.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Doug Ledford <dledford@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jason Wang <jasowang@...hat.com>, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, Maor Gottlieb <maorg@...dia.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
        Saeed Mahameed <saeedm@...dia.com>,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH mlx5-next 1/7] RDMA/mlx5: Don't set esc_size in user mr

On Tue, Oct 12, 2021 at 04:57:16PM +0300, Aharon Landau wrote:
> 
> On 10/12/2021 3:52 PM, Jason Gunthorpe wrote:
> > On Tue, Oct 12, 2021 at 01:26:29PM +0300, Leon Romanovsky wrote:
> > > From: Aharon Landau <aharonl@...dia.com>
> > > 
> > > reg_create() is used for user MRs only and should not set desc_size at
> > > all. Attempt to set it causes to the following trace:
> > > 
> > > BUG: unable to handle page fault for address: 0000000800000000
> > > PGD 0 P4D 0
> > > Oops: 0000 [#1] SMP PTI
> > > CPU: 5 PID: 890 Comm: ib_write_bw Not tainted 5.15.0-rc4+ #47
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> > > RIP: 0010:mlx5_ib_dereg_mr+0x14/0x3b0 [mlx5_ib]
> > > Code: 48 63 cd 4c 89 f7 48 89 0c 24 e8 37 30 03 e1 48 8b 0c 24 eb a0 90 0f 1f 44 00 00 41 56 41 55 41 54 55 53 48 89 fb 48 83 ec 30 <48> 8b 2f 65 48 8b 04 25 28 00 00 00 48 89 44 24 28 31 c0 8b 87 c8
> > > RSP: 0018:ffff88811afa3a60 EFLAGS: 00010286
> > > RAX: 000000000000001c RBX: 0000000800000000 RCX: 0000000000000000
> > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000800000000
> > > RBP: 0000000800000000 R08: 0000000000000000 R09: c0000000fffff7ff
> > > R10: ffff88811afa38f8 R11: ffff88811afa38f0 R12: ffffffffa02c7ac0
> > > R13: 0000000000000000 R14: ffff88811afa3cd8 R15: ffff88810772fa00
> > > FS:  00007f47b9080740(0000) GS:ffff88852cd40000(0000) knlGS:0000000000000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000000800000000 CR3: 000000010761e003 CR4: 0000000000370ea0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > Call Trace:
> > >   mlx5_ib_free_odp_mr+0x95/0xc0 [mlx5_ib]
> > >   mlx5_ib_dereg_mr+0x128/0x3b0 [mlx5_ib]
> > >   ib_dereg_mr_user+0x45/0xb0 [ib_core]
> > >   ? xas_load+0x8/0x80
> > >   destroy_hw_idr_uobject+0x1a/0x50 [ib_uverbs]
> > >   uverbs_destroy_uobject+0x2f/0x150 [ib_uverbs]
> > >   uobj_destroy+0x3c/0x70 [ib_uverbs]
> > >   ib_uverbs_cmd_verbs+0x467/0xb00 [ib_uverbs]
> > >   ? uverbs_finalize_object+0x60/0x60 [ib_uverbs]
> > >   ? ttwu_queue_wakelist+0xa9/0xe0
> > >   ? pty_write+0x85/0x90
> > >   ? file_tty_write.isra.33+0x214/0x330
> > >   ? process_echoes+0x60/0x60
> > >   ib_uverbs_ioctl+0xa7/0x110 [ib_uverbs]
> > >   __x64_sys_ioctl+0x10d/0x8e0
> > >   ? vfs_write+0x17f/0x260
> > >   do_syscall_64+0x3c/0x80
> > >   entry_SYSCALL_64_after_hwframe+0x44/0xae
> > > 
> > > Fixes: a639e66703ee ("RDMA/mlx5: Zero out ODP related items in the mlx5_ib_mr")
> > Can you explain why this is crashing?
> > 
> > reg_create isn't used on the ODP implicit children path.
> > 
> > Jason
> It is not implicit ODP flow, therefore, mr->implicit_children shouldn't be
> set.

It should always be initialized. That seems to be the bug here, add the
missing xa_init as well as delete the extra desc_size set:

diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c
index b4d2322e9ca564..46626e0fe08905 100644
--- a/drivers/infiniband/hw/mlx5/mr.c
+++ b/drivers/infiniband/hw/mlx5/mr.c
@@ -1525,6 +1525,7 @@ static struct ib_mr *create_user_odp_mr(struct ib_pd *pd, u64 start, u64 length,
                ib_umem_release(&odp->umem);
                return ERR_CAST(mr);
        }
+       xa_init(&mr->implicit_children);
 
        odp->private = mr;
        err = mlx5r_store_odp_mkey(dev, &mr->mmkey);

Jason