Message-ID:
 <CY8PR12MB71958C150D7604EAD4463F4ADCC72@CY8PR12MB7195.namprd12.prod.outlook.com>
Date: Fri, 21 Feb 2025 03:14:16 +0000
From: Parav Pandit <parav@...lanox.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>, Jason Gunthorpe <jgg@...pe.ca>
CC: Leon Romanovsky <leon@...nel.org>, Maher Sanalla <msanalla@...dia.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] RDMA/core: fix a NULL-pointer dereference in
 hw_stat_device_show()


> From: Roman Gushchin <roman.gushchin@...ux.dev>
> Sent: Friday, February 21, 2025 7:36 AM
> 
> Commit 54747231150f ("RDMA: Introduce and use rdma_device_to_ibdev()")
> introduced rdma_device_to_ibdev() helper which has to be used to obtain an
> ib_device pointer from a device pointer.
>
 
> hw_stat_device_show() and hw_stat_device_store() were missed.
> 
> It causes a NULL pointer dereference panic on an attempt to read hw counters
> from a namespace, when the device structure is not embedded into the
> ib_device structure. 
Do you mean net namespace other than default init_net?
Assuming the answer is yes, some question below.

> In this case casting the device pointer into the ib_device
> pointer using container_of() is wrong.
> Instead, rdma_device_to_ibdev() should be used, which uses the back-
> reference (container_of(device, struct ib_core_device, dev))->owner.
> 
> [42021.807566] BUG: kernel NULL pointer dereference, address:
> 0000000000000028 [42021.814463] #PF: supervisor read access in kernel
> mode [42021.819549] #PF: error_code(0x0000) - not-present page
> [42021.824636] PGD 0 P4D 0 [42021.827145] Oops: 0000 [#1] SMP PTI
> [42021.830598] CPU: 82 PID: 2843922 Comm: switchto-defaul Kdump: loaded
> Tainted: G S      W I        XXX
> [42021.841697] Hardware name: XXX
> [42021.849619] RIP: 0010:hw_stat_device_show+0x1e/0x40 [ib_core]
> [42021.855362] Code: 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f
> 44 00 00 49 89 d0 4c 8b 5e 20 48 8b 8f b8 04 00 00 48 81 c7 f0 fa ff ff <48> 8b
> 41 28 48 29 ce 48 83 c6 d0 48 c1 ee 04 69 d6 ab aa aa aa 48 [42021.873931]
> RSP: 0018:ffff97fe90f03da0 EFLAGS: 00010287 [42021.879108] RAX:
> ffff9406988a8c60 RBX: ffff940e1072d438 RCX: 0000000000000000
> [42021.886169] RDX: ffff94085f1aa000 RSI: ffff93c6cbbdbcb0 RDI:
> ffff940c7517aef0 [42021.893230] RBP: ffff97fe90f03e70 R08:
> ffff94085f1aa000 R09: 0000000000000000 [42021.900294] R10:
> ffff94085f1aa000 R11: ffffffffc0775680 R12: ffffffff87ca2530 [42021.907355]
> R13: ffff940651602840 R14: ffff93c6cbbdbcb0 R15: ffff94085f1aa000
> [42021.914418] FS:  00007fda1a3b9700(0000) GS:ffff94453fb80000(0000)
> knlGS:0000000000000000 [42021.922423] CS:  0010 DS: 0000 ES: 0000 CR0:
> 0000000080050033 [42021.928130] CR2: 0000000000000028 CR3:
> 00000042dcfb8003 CR4: 00000000003726f0 [42021.935194] DR0:
> 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [42021.942257] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
> 0000000000000400 [42021.949324] Call Trace:
> [42021.951756]  <TASK>
> [42021.953842]  [<ffffffff86c58674>] ? show_regs+0x64/0x70 [42021.959030]
> [<ffffffff86c58468>] ? __die+0x78/0xc0 [42021.963874]  [<ffffffff86c9ef75>] ?
> page_fault_oops+0x2b5/0x3b0 [42021.969749]  [<ffffffff87674b92>] ?
> exc_page_fault+0x1a2/0x3c0 [42021.975549]  [<ffffffff87801326>] ?
> asm_exc_page_fault+0x26/0x30 [42021.981517]  [<ffffffffc0775680>] ?
> __pfx_show_hw_stats+0x10/0x10 [ib_core] [42021.988482]
> [<ffffffffc077564e>] ? hw_stat_device_show+0x1e/0x40 [ib_core]
> [42021.995438]  [<ffffffff86ac7f8e>] dev_attr_show+0x1e/0x50
> [42022.000803]  [<ffffffff86a3eeb1>] sysfs_kf_seq_show+0x81/0xe0
> [42022.006508]  [<ffffffff86a11134>] seq_read_iter+0xf4/0x410
> [42022.011954]  [<ffffffff869f4b2e>] vfs_read+0x16e/0x2f0 [42022.017058]
> [<ffffffff869f50ee>] ksys_read+0x6e/0xe0 [42022.022073]  [<ffffffff8766f1ca>]
> do_syscall_64+0x6a/0xa0 [42022.027441]  [<ffffffff8780013b>]
> entry_SYSCALL_64_after_hwframe+0x78/0xe2
> 
> Fixes: 54747231150f ("RDMA: Introduce and use rdma_device_to_ibdev()")
Commit eb15c78b05bd9 eliminated hw_counters sysfs directory into the net namespace.
I don't see it created in any other net ns other than init_net with kernel 6.12+.

I am puzzled. Can you please explain/share the reproduction steps for generating above call trace?
 
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: Maher Sanalla <msanalla@...dia.com>
> Cc: Parav Pandit <parav@...lanox.com>
> Cc: linux-rdma@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/infiniband/core/sysfs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index 7491328ca5e6..0be77b8abeae 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -148,7 +148,7 @@ static ssize_t hw_stat_device_show(struct device
> *dev,  {
>  	struct hw_stats_device_attribute *stat_attr =
>  		container_of(attr, struct hw_stats_device_attribute, attr);
> -	struct ib_device *ibdev = container_of(dev, struct ib_device, dev);
> +	struct ib_device *ibdev = rdma_device_to_ibdev(dev);
> 
>  	return stat_attr->show(ibdev, ibdev->hw_stats_data->stats,
>  			       stat_attr - ibdev->hw_stats_data->attrs, 0, buf);
> @@ -160,7 +160,7 @@ static ssize_t hw_stat_device_store(struct device
> *dev,  {
>  	struct hw_stats_device_attribute *stat_attr =
>  		container_of(attr, struct hw_stats_device_attribute, attr);
> -	struct ib_device *ibdev = container_of(dev, struct ib_device, dev);
> +	struct ib_device *ibdev = rdma_device_to_ibdev(dev);
> 
>  	return stat_attr->store(ibdev, ibdev->hw_stats_data->stats,
>  				stat_attr - ibdev->hw_stats_data->attrs, 0,
> buf,
> --
> 2.48.1.601.g30ceb7b040-goog

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