From nobody Fri Apr 17 12:01:31 2026 Received: from azure-sdnproxy.icoremail.net (azure-sdnproxy.icoremail.net [52.229.168.213]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7229232549E; Thu, 19 Feb 2026 12:47:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.229.168.213 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771505236; cv=none; b=KYu/UAHPUz4cxykeUQyUdxOTMqAZ3N0LPx2Hse4em7+gSAI51VnmxRY+iFiqRRe7plN6tl0JW+3ec7MbE/Tvn7sKHLfqkDbTyrCg6SFqCRauOKMmm594eLDuW1zE4a8BEoP66lp/zHMdQE3a5ivIJSyfT/Cq3cqNuay76DBWANk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771505236; c=relaxed/simple; bh=mQfYg9NSAHTeK900iLMcrRSQ5v+Qpu2cCZ21kYqMhic=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=TShJ7g0OSE8KS2PvoY+6TARZVSVHiDDbdrpEKUFdeahDfHzEqcJYxt6R88xyCQxAxB894xhkBWj3ee3ypMK+aKPuHrFifOd8fboOLDu0Qz9+hZxhbr8+ZL7IwoVyD+7a/gxUVViSX16XHlwIr6ExCRmBLqxR6dMRQ2LGY6iABOs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=zju.edu.cn; spf=pass smtp.mailfrom=zju.edu.cn; arc=none smtp.client-ip=52.229.168.213 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=zju.edu.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zju.edu.cn Received: from zju.edu.cn (unknown [218.12.18.79]) by mtasvr (Coremail) with SMTP id _____wDn7VEzBpdpJNXCAA--.25819S3; Thu, 19 Feb 2026 20:46:44 +0800 (CST) Received: from ubuntu.localdomain (unknown [218.12.18.79]) by mail-app3 (Coremail) with SMTP id zS_KCgBHSWwuBpdpQ8dKBg--.41083S2; Thu, 19 Feb 2026 20:46:42 +0800 (CST) From: Duoming Zhou To: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kevin.curtis@farsite.co.uk, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, Duoming Zhou Subject: [PATCH net] net: wan: farsync: Fix use-after-free bugs caused by unfinished tasklets Date: Thu, 19 Feb 2026 20:46:37 +0800 Message-Id: <20260219124637.72578-1-duoming@zju.edu.cn> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: zS_KCgBHSWwuBpdpQ8dKBg--.41083S2 X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/1tbiAwYHAWmWFggBKgA8s1 X-CM-DELIVERINFO: =?B?zaqsKgXKKxbFmtjJiESix3B1w3uoVhYI+vyen2ZzBEkOnu5chDpkB+ZdGnv/zQ0PbP CR1zEltBcmylrpStgRg1rf41SCVEefaMrEZEZGt+jAKGCSGVKomGclygUyIahAa5OYjXgz JJLQ1wXn7s6o5WA1cuJbe7CMdXN57FLLllTvMWPIi25tfpAfBJsFVs3Fx8myig== X-Coremail-Antispam: 1Uk129KBj93XoWxKryruryUWw17Ww1kZFyDtwc_yoW7Cw17pa nxArWxCrW8Jryjqr47Jr48Gr18JFWDAa4UKrW8Cr12v3Wrur15tr1UJF45Zr1UKrWrAFy7 J3ZxJrWUKr1UJwcCm3ZEXasCq-sJn29KB7ZKAUJUUUUU529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUvvb4IE77IF4wAFF20E14v26r4j6ryUM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_tr0E3s1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr1j6F4UJwA2z4x0Y4vEx4A2jsIE14v26rxl6s0DM28EF7xvwVC2z280aVCY1x0267AK xVW0oVCq3wAS0I0E0xvYzxvE52x082IY62kv0487Mc804VCY07AIYIkI8VC2zVCFFI0UMc 02F40EFcxC0VAKzVAqx4xG6I80ewAv7VC0I7IYx2IY67AKxVWUJVWUGwAv7VC2z280aVAF wI0_Jr0_Gr1lOx8S6xCaFVCjc4AY6r1j6r4UM4x0Y48IcxkI7VAKI48JM4x0Y48IcxkI7V AKI48G6xCjnVAKz4kxMxAIw28IcxkI7VAKI48JMxC20s026xCaFVCjc4AY6r1j6r4UMI8I 3I0E5I8CrVAFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxV WUtVW8ZwCIc40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1j6r1xMIIF0xvE2Ix0cI8I cVCY1x0267AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aV AFwI0_Jr0_Gr1lIxAIcVC2z280aVCY1x0267AKxVWUJVW8JbIYCTnIWIevJa73UjIFyTuY vjxU7xwIDUUUU Content-Type: text/plain; charset="utf-8" When the FarSync T-series card is being detached, the fst_card_info is deallocated in fst_remove_one(). However, the fst_tx_task or fst_int_task may still be running or pending, leading to use-after-free bugs when the already freed fst_card_info is accessed in fst_process_tx_work_q() or fst_process_int_work_q(). A typical race condition is depicted below: CPU 0 (cleanup) | CPU 1 (tasklet) | fst_start_xmit() fst_remove_one() | tasklet_schedule() unregister_hdlc_device()| | fst_process_tx_work_q() //handler kfree(card) //free | do_bottom_half_tx() | card-> //use The following KASAN trace was captured: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D BUG: KASAN: slab-use-after-free in do_bottom_half_tx+0xb88/0xd00 Read of size 4 at addr ffff88800aad101c by task ksoftirqd/3/32 ... Call Trace: dump_stack_lvl+0x55/0x70 print_report+0xcb/0x5d0 ? do_bottom_half_tx+0xb88/0xd00 kasan_report+0xb8/0xf0 ? do_bottom_half_tx+0xb88/0xd00 do_bottom_half_tx+0xb88/0xd00 ? _raw_spin_lock_irqsave+0x85/0xe0 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? __pfx___hrtimer_run_queues+0x10/0x10 fst_process_tx_work_q+0x67/0x90 tasklet_action_common+0x1fa/0x720 ? hrtimer_interrupt+0x31f/0x780 handle_softirqs+0x176/0x530 __irq_exit_rcu+0xab/0xe0 sysvec_apic_timer_interrupt+0x70/0x80 ... Allocated by task 41 on cpu 3 at 72.330843s: kasan_save_stack+0x24/0x50 kasan_save_track+0x17/0x60 __kasan_kmalloc+0x7f/0x90 fst_add_one+0x1a5/0x1cd0 local_pci_probe+0xdd/0x190 pci_device_probe+0x341/0x480 really_probe+0x1c6/0x6a0 __driver_probe_device+0x248/0x310 driver_probe_device+0x48/0x210 __device_attach_driver+0x160/0x320 bus_for_each_drv+0x101/0x190 __device_attach+0x198/0x3a0 device_initial_probe+0x78/0xa0 pci_bus_add_device+0x81/0xc0 pci_bus_add_devices+0x7e/0x190 enable_slot+0x9b9/0x1130 acpiphp_check_bridge.part.0+0x2e1/0x460 acpiphp_hotplug_notify+0x36c/0x3c0 acpi_device_hotplug+0x203/0xb10 acpi_hotplug_work_fn+0x59/0x80 ... Freed by task 41 on cpu 1 at 75.138639s: kasan_save_stack+0x24/0x50 kasan_save_track+0x17/0x60 kasan_save_free_info+0x3b/0x60 __kasan_slab_free+0x43/0x70 kfree+0x135/0x410 fst_remove_one+0x2ca/0x540 pci_device_remove+0xa6/0x1d0 device_release_driver_internal+0x364/0x530 pci_stop_bus_device+0x105/0x150 pci_stop_and_remove_bus_device+0xd/0x20 disable_slot+0x116/0x260 acpiphp_disable_and_eject_slot+0x4b/0x190 acpiphp_hotplug_notify+0x230/0x3c0 acpi_device_hotplug+0x203/0xb10 acpi_hotplug_work_fn+0x59/0x80 ... The buggy address belongs to the object at ffff88800aad1000 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 28 bytes inside of freed 1024-byte region The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xaad0 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0x100000000000040(head|node=3D0|zone=3D1) page_type: f5(slab) raw: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000 raw: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 0100000000000040 ffff888007042dc0 dead000000000122 0000000000000000 head: 0000000000000000 0000000080100010 00000000f5000000 0000000000000000 head: 0100000000000003 ffffea00002ab401 00000000ffffffff 00000000ffffffff head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88800aad0f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff88800aad0f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff88800aad1000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88800aad1080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88800aad1100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Fix this by ensuring that both fst_tx_task and fst_int_task are properly canceled before the fst_card_info is released. Add tasklet_kill() in fst_remove_one() to synchronize with any pending or running tasklets. Since unregister_hdlc_device() stops data transmission and reception, and fst_disable_intr() prevents further interrupts, it is appropriate to place tasklet_kill() after these calls. The bugs were identified through static analysis. To reproduce the issue and validate the fix, a FarSync T-series card was simulated in QEMU and delays(e.g., mdelay()) were introduced within the tasklet handler to increase the likelihood of triggering the race condition. Fixes: 2f623aaf9f31 ("net: farsync: Fix kmemleak when rmmods farsync") Signed-off-by: Duoming Zhou Reviewed-by: Jijie Shao --- drivers/net/wan/farsync.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/wan/farsync.c b/drivers/net/wan/farsync.c index 5b01642ca44..6b2d1e63855 100644 --- a/drivers/net/wan/farsync.c +++ b/drivers/net/wan/farsync.c @@ -2550,6 +2550,8 @@ fst_remove_one(struct pci_dev *pdev) =20 fst_disable_intr(card); free_irq(card->irq, card); + tasklet_kill(&fst_tx_task); + tasklet_kill(&fst_int_task); =20 iounmap(card->ctlmem); iounmap(card->mem); --=20 2.34.1