From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Kees Cook <keescook@chromium.org>, Jakub Kicinski <kuba@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
netdev@vger.kernel.org, linux-hardening@vger.kernel.org,
Simon Horman <horms@kernel.org>, Jiri Pirko <jiri@resnulli.us>,
Daniel Borkmann <daniel@iogearbox.net>,
Coco Li <lixiaoyan@google.com>,
Amritha Nambiar <amritha.nambiar@intel.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] netdev: Use flexible array for trailing private bytes
Date: Thu, 29 Feb 2024 16:15:12 -0600 [thread overview]
Message-ID: <93cbd0a3-60cf-400f-a05c-f81dc3d8c75d@embeddedor.com> (raw)
In-Reply-To: <20240229213018.work.556-kees@kernel.org>
On 2/29/24 15:30, Kees Cook wrote:
> Introduce a new struct net_device_priv that contains struct net_device
> but also accounts for the commonly trailing bytes through the "size" and
> "data" members. As many dummy struct net_device instances exist still,
> it is non-trivial to but this flexible array inside struct net_device
> itself. But we can add a sanity check in netdev_priv() to catch any
> attempts to access the private data of a dummy struct.
>
> Adjust allocation logic to use the new full structure.
>
> Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
[for the flex `struct net_device_priv`, `struct_size()`, `__counted_by()`,
and the use of `container_of()` to retrieve a pointer to the flex struct
and return pointer to flex-array member `data` in `netdev_priv()`]
Thanks
--
Gustavo
> ---
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: netdev@vger.kernel.org
> Cc: linux-hardening@vger.kernel.org
> ---
> include/linux/netdevice.h | 21 ++++++++++++++++++---
> net/core/dev.c | 12 ++++--------
> 2 files changed, 22 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 118c40258d07..b476809d0bae 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -1815,6 +1815,8 @@ enum netdev_stat_type {
> NETDEV_PCPU_STAT_DSTATS, /* struct pcpu_dstats */
> };
>
> +#define NETDEV_ALIGN 32
> +
> /**
> * struct net_device - The DEVICE structure.
> *
> @@ -2476,6 +2478,14 @@ struct net_device {
> struct hlist_head page_pools;
> #endif
> };
> +
> +struct net_device_priv {
> + struct net_device dev;
> + u32 size;
> + u8 data[] __counted_by(size)
> + __aligned(NETDEV_ALIGN);
> +};
> +
> #define to_net_dev(d) container_of(d, struct net_device, dev)
>
> /*
> @@ -2496,8 +2506,6 @@ static inline bool netif_elide_gro(const struct net_device *dev)
> return false;
> }
>
> -#define NETDEV_ALIGN 32
> -
> static inline
> int netdev_get_prio_tc_map(const struct net_device *dev, u32 prio)
> {
> @@ -2665,7 +2673,14 @@ void dev_net_set(struct net_device *dev, struct net *net)
> */
> static inline void *netdev_priv(const struct net_device *dev)
> {
> - return (char *)dev + ALIGN(sizeof(struct net_device), NETDEV_ALIGN);
> + struct net_device_priv *priv;
> +
> + /* Dummy struct net_device have no trailing data. */
> + if (WARN_ON_ONCE(dev->reg_state == NETREG_DUMMY))
> + return NULL;
> +
> + priv = container_of(dev, struct net_device_priv, dev);
> + return (u8 *)priv->data;
> }
>
> /* Set the sysfs physical device reference for the network logical device
> diff --git a/net/core/dev.c b/net/core/dev.c
> index cb2dab0feee0..0fcaf6ae8486 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -10800,7 +10800,7 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
> {
> struct net_device *dev;
> unsigned int alloc_size;
> - struct net_device *p;
> + struct net_device_priv *p;
>
> BUG_ON(strlen(name) >= sizeof(dev->name));
>
> @@ -10814,20 +10814,16 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,
> return NULL;
> }
>
> - alloc_size = sizeof(struct net_device);
> - if (sizeof_priv) {
> - /* ensure 32-byte alignment of private area */
> - alloc_size = ALIGN(alloc_size, NETDEV_ALIGN);
> - alloc_size += sizeof_priv;
> - }
> + alloc_size = struct_size(p, data, sizeof_priv);
> /* ensure 32-byte alignment of whole construct */
> alloc_size += NETDEV_ALIGN - 1;
>
> p = kvzalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
> if (!p)
> return NULL;
> + p->size = sizeof_priv;
>
> - dev = PTR_ALIGN(p, NETDEV_ALIGN);
> + dev = &PTR_ALIGN(p, NETDEV_ALIGN)->dev;
> dev->padded = (char *)dev - (char *)p;
>
> ref_tracker_dir_init(&dev->refcnt_tracker, 128, name);
next prev parent reply other threads:[~2024-02-29 22:15 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-29 21:30 [PATCH] netdev: Use flexible array for trailing private bytes Kees Cook
2024-02-29 22:15 ` Gustavo A. R. Silva [this message]
2024-03-01 6:59 ` Jakub Kicinski
2024-03-01 8:03 ` Eric Dumazet
2024-03-01 12:58 ` Alexander Lobakin
2024-03-01 13:25 ` Eric Dumazet
2024-03-01 14:30 ` Alexander Lobakin
2024-03-01 17:35 ` Jakub Kicinski
2024-03-04 14:32 ` Alexander Lobakin
2024-03-04 15:24 ` Jakub Kicinski
2024-03-01 11:41 ` Greg KH
2024-03-06 13:16 ` Breno Leitao
2024-03-06 15:06 ` Jakub Kicinski
2024-03-06 23:42 ` Kees Cook
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