Re: [PATCH mlx5-next 1/7] RDMA/mlx5: Don't set esc_size in user mr

[Aharon Landau]

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@xxxxxxxxxx>
> >
> > 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.

desc_size shares the same union with implicit_children, and setting it 
leads to a wrong iteration.

Aharon