RE: [PATCH] RDMA/core: don't expose hw_counters outside of init net namespace

Parav Pandit
2025-02-27T05:23:02Z

> From: Roman Gushchin <roman.gushchin@linux.dev>
> Sent: Thursday, February 27, 2025 12:32 AM
>
> Commit 5fd8529350f0 ("RDMA/core: fix a NULL-pointer dereference in
> hw_stat_device_show()") accidentally almost exposed hw counters to non-init
> net namespaces. It didn't expose them fully, as an attempt to read any of
> those counters leads to a crash like this one:
>
It is not the commit 5fd8529350f0.
You just want to say cited commit accidentally..

> [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
>
> The problem can be reproduced using the following steps:
> ip netns add foo
> ip netns exec foo bash
> cat /sys/class/infiniband/mlx4_0/hw_counters/*
>
> The panic occurs because of casting the device pointer into an ib_device
> pointer using container_of() in hw_stat_device_show() is wrong and leads to a
> memory corruption.
>
> However the real problem is that hw counters should never been exposed
> outside of the non-init net namespace.
>
> Fix this by saving the index of the corresponding attribute group (it might be 1
> or 2 depending on the presence of driver-specific
> attributes) and zeroing the pointer to hw_counters group for compat devices
> during the initialization.
>
> With this fix applied hw_counters are not available in a non-init net
> namespace:
> find /sys/class/infiniband/mlx4_0/ -name hw_counters
> /sys/class/infiniband/mlx4_0/ports/1/hw_counters
> /sys/class/infiniband/mlx4_0/ports/2/hw_counters
> /sys/class/infiniband/mlx4_0/hw_counters
>
> ip netns add foo
> ip netns exec foo bash
> find /sys/class/infiniband/mlx4_0/ -name hw_counters
>
> Fixes: 467f432a521a ("RDMA/core: Split port and device counter sysfs
> attributes")
> Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Maher Sanalla <msanalla@nvidia.com>
> Cc: Parav Pandit <parav@mellanox.com>
> Cc: linux-rdma@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
> drivers/infiniband/core/device.c | 9 +++++++++
> drivers/infiniband/core/sysfs.c | 1 +
> include/rdma/ib_verbs.h | 1 +
> 3 files changed, 11 insertions(+)
>
> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> index 0ded91f056f3..8feb22089cbb 100644
> --- a/drivers/infiniband/core/device.c
> +++ b/drivers/infiniband/core/device.c
> @@ -528,6 +528,8 @@ static struct class ib_class = { static void
> rdma_init_coredev(struct ib_core_device *coredev,
> struct ib_device *dev, struct net *net) {
> + bool is_full_dev = &dev->coredev == coredev;
> +
> /* This BUILD_BUG_ON is intended to catch layout change
> * of union of ib_core_device and device.
> * dev must be the first element as ib_core and providers @@ -539,6
> +541,13 @@ static void rdma_init_coredev(struct ib_core_device *coredev,
>
> coredev->dev.class = &ib_class;
> coredev->dev.groups = dev->groups;
> +
> + /*
> + * Don't expose hw counters outside of the init namespace.
> + */
> + if (!is_full_dev && dev->hw_stats_attr_index)
> + coredev->dev.groups[dev->hw_stats_attr_index] = NULL;
> +
> device_initialize(&coredev->dev);
> coredev->owner = dev;
> INIT_LIST_HEAD(&coredev->port_list);
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index 7491328ca5e6..0ed862b38b44 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -976,6 +976,7 @@ int ib_setup_device_attrs(struct ib_device *ibdev)
> for (i = 0; i != ARRAY_SIZE(ibdev->groups); i++)
> if (!ibdev->groups[i]) {
> ibdev->groups[i] = &data->group;
> + ibdev->hw_stats_attr_index = i;
> return 0;
> }
> WARN(true, "struct ib_device->groups is too small"); diff --git
> a/include/rdma/ib_verbs.h b/include/rdma/ib_verbs.h index
> b59bf30de430..a5761038935d 100644
> --- a/include/rdma/ib_verbs.h
> +++ b/include/rdma/ib_verbs.h
> @@ -2767,6 +2767,7 @@ struct ib_device {
> * It is a NULL terminated array.
> */
> const struct attribute_group *groups[4];
> + u8 hw_stats_attr_index;
>
> u64 uverbs_cmd_mask;
>
> --
> 2.48.1.711.g2feabab25a-goog

With above suggested small commit log correction,
Reviewed-by: Parav Pandit <parav@nvidia.com>