netdev - Re: [PATCH net 4/6] lib: objagg: Fix general protection fault

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Date: Sat, 8 Jun 2024 10:01:35 +0100
From: Simon Horman <horms@...nel.org>
To: Petr Machata <petrm@...dia.com>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, Amit Cohen <amcohen@...dia.com>,
	Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...nulli.us>,
	Alexander Zubkov <green@...tor.net>, mlxsw@...dia.com
Subject: Re: [PATCH net 4/6] lib: objagg: Fix general protection fault

On Thu, Jun 06, 2024 at 04:49:41PM +0200, Petr Machata wrote:
> From: Ido Schimmel <idosch@...dia.com>
> 
> The library supports aggregation of objects into other objects only if
> the parent object does not have a parent itself. That is, nesting is not
> supported.
> 
> Aggregation happens in two cases: Without and with hints, where hints
> are a pre-computed recommendation on how to aggregate the provided
> objects.
> 
> Nesting is not possible in the first case due to a check that prevents
> it, but in the second case there is no check because the assumption is
> that nesting cannot happen when creating objects based on hints. The
> violation of this assumption leads to various warnings and eventually to
> a general protection fault [1].
> 
> Before fixing the root cause, error out when nesting happens and warn.
> 
> [1]
> general protection fault, probably for non-canonical address 0xdead000000000d90: 0000 [#1] PREEMPT SMP PTI
> CPU: 1 PID: 1083 Comm: kworker/1:9 Tainted: G        W          6.9.0-rc6-custom-gd9b4f1cca7fb #7
> Hardware name: Mellanox Technologies Ltd. MSN3700/VMOD0005, BIOS 5.11 01/06/2019
> Workqueue: mlxsw_core mlxsw_sp_acl_tcam_vregion_rehash_work
> RIP: 0010:mlxsw_sp_acl_erp_bf_insert+0x25/0x80
> [...]
> Call Trace:
>  <TASK>
>  mlxsw_sp_acl_atcam_entry_add+0x256/0x3c0
>  mlxsw_sp_acl_tcam_entry_create+0x5e/0xa0
>  mlxsw_sp_acl_tcam_vchunk_migrate_one+0x16b/0x270
>  mlxsw_sp_acl_tcam_vregion_rehash_work+0xbe/0x510
>  process_one_work+0x151/0x370
>  worker_thread+0x2cb/0x3e0
>  kthread+0xd0/0x100
>  ret_from_fork+0x34/0x50
>  ret_from_fork_asm+0x1a/0x30
>  </TASK>
> 
> Fixes: 9069a3817d82 ("lib: objagg: implement optimization hints assembly and use hints for object creation")
> Reported-by: Alexander Zubkov <green@...tor.net>
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> Reviewed-by: Amit Cohen <amcohen@...dia.com>
> Tested-by: Alexander Zubkov <green@...tor.net>
> Signed-off-by: Petr Machata <petrm@...dia.com>

Reviewed-by: Simon Horman <horms@...nel.org>