From: Simon Horman <horms@kernel.org>
To: Chengfeng Ye <nicoyip.dev@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Thorsten Blum <thorsten.blum@linux.dev>,
Andrew Morton <akpm@linux-foundation.org>,
Andy Shevchenko <andriy.shevchenko@intel.com>,
Randy Dunlap <rdunlap@infradead.org>,
Robert Olsson <robert.olsson@its.uu.se>,
Stephen Hemminger <stephen@networkplumber.org>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] net: pktgen: fix proc entry use-after-free
Date: Fri, 24 Jul 2026 14:24:48 +0100 [thread overview]
Message-ID: <20260724132448.GK418547@horms.kernel.org> (raw)
In-Reply-To: <20260719145740.2888967-1-nicoyip.dev@gmail.com>
On Sun, Jul 19, 2026 at 10:57:40PM +0800, Chengfeng Ye wrote:
> pktgen_change_name() replaces pkt_dev->entry while holding t->if_lock.
> pktgen_remove_device() removes the same entry before
> _rem_dev_from_if_list() takes that lock.
>
> This allows the following interleaving:
>
> CPU 0 (NETDEV_CHANGENAME) CPU 1 (kpktgend)
> if_lock(t)
> proc_remove(pkt_dev->entry)
> proc_remove(pkt_dev->entry)
> pkt_dev->entry = proc_create_data(...)
> if_unlock(t)
>
> The kthread can pass the stale proc_dir_entry to proc_remove() after the
> rename path has freed it. A reproducer with a widened race window reports:
>
> BUG: KASAN: slab-use-after-free in proc_remove+0x78/0x80
> Read of size 8 at addr ffff8881478fea70 by task kpktgend_0/67
> Call Trace:
> proc_remove+0x78/0x80
> pktgen_remove_device.isra.0+0x11c/0x4c0
> pktgen_thread_worker+0x1214/0x6bc0
> kthread+0x2c6/0x3b0
> Allocated by task 95:
> __proc_create+0x204/0x790
> proc_create_data+0x72/0xe0
> pktgen_thread_write+0xd61/0x1510
> Freed by task 28:
> kmem_cache_free+0xcb/0x3d0
> proc_free_inode+0x5b/0x80
> rcu_core+0x50a/0x1850
> The buggy address belongs to the object at ffff8881478fea00
> which belongs to the cache proc_dir_entry of size 192
>
> Move proc_remove() into the if_lock-protected list removal helper. Keep it
> before list_del_rcu() to preserve the ordering required by add_device().
> The rename path must then finish replacing the entry before removal, or
> it observes that the device is no longer on the list.
>
> Fixes: 39df232f1a9b ("[PKTGEN]: fix device name handling")
> Cc: stable@vger.kernel.org
> Signed-off-by: Chengfeng Ye <nicoyip.dev@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
prev parent reply other threads:[~2026-07-24 13:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-19 14:57 [PATCH] net: pktgen: fix proc entry use-after-free Chengfeng Ye
2026-07-24 13:24 ` Simon Horman [this message]
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