lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 19 Jul 2022 16:53:24 -0300 From: "Guilherme G. Piccoli" <gpiccoli@...lia.com> To: akpm@...ux-foundation.org, bhe@...hat.com, pmladek@...e.com, kexec@...ts.infradead.org Cc: linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org, netdev@...r.kernel.org, x86@...nel.org, kernel-dev@...lia.com, kernel@...ccoli.net, halves@...onical.com, fabiomirmar@...il.com, alejandro.j.jimenez@...cle.com, andriy.shevchenko@...ux.intel.com, arnd@...db.de, bp@...en8.de, corbet@....net, d.hatayama@...fujitsu.com, dave.hansen@...ux.intel.com, dyoung@...hat.com, feng.tang@...el.com, gregkh@...uxfoundation.org, mikelley@...rosoft.com, hidehiro.kawai.ez@...achi.com, jgross@...e.com, john.ogness@...utronix.de, keescook@...omium.org, luto@...nel.org, mhiramat@...nel.org, mingo@...hat.com, paulmck@...nel.org, peterz@...radead.org, rostedt@...dmis.org, senozhatsky@...omium.org, stern@...land.harvard.edu, tglx@...utronix.de, vgoyal@...hat.com, vkuznets@...hat.com, will@...nel.org, "Guilherme G. Piccoli" <gpiccoli@...lia.com>, Andrea Parri <parri.andrea@...il.com>, Dexuan Cui <decui@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, Stephen Hemminger <sthemmin@...rosoft.com>, Tianyu Lan <Tianyu.Lan@...rosoft.com>, Wei Liu <wei.liu@...nel.org> Subject: [PATCH v2 11/13] video/hyperv_fb: Avoid taking busy spinlock on panic path The Hyper-V framebuffer code registers a panic notifier in order to try updating its fbdev if the kernel crashed. The notifier callback is straightforward, but it calls the vmbus_sendpacket() routine eventually, and such function takes a spinlock for the ring buffer operations. Panic path runs in atomic context, with local interrupts and preemption disabled, and all secondary CPUs shutdown. That said, taking a spinlock might cause a lockup if a secondary CPU was disabled with such lock taken. Fix it here by checking if the ring buffer spinlock is busy on Hyper-V framebuffer panic notifier; if so, bail-out avoiding the potential lockup scenario. Cc: Andrea Parri (Microsoft) <parri.andrea@...il.com> Cc: Dexuan Cui <decui@...rosoft.com> Cc: Haiyang Zhang <haiyangz@...rosoft.com> Cc: "K. Y. Srinivasan" <kys@...rosoft.com> Cc: Michael Kelley <mikelley@...rosoft.com> Cc: Stephen Hemminger <sthemmin@...rosoft.com> Cc: Tianyu Lan <Tianyu.Lan@...rosoft.com> Cc: Wei Liu <wei.liu@...nel.org> Tested-by: Fabio A M Martins <fabiomirmar@...il.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@...lia.com> --- V2: - new patch, based on the discussion in [0]. [0] https://lore.kernel.org/lkml/2787b476-6366-1c83-db80-0393da417497@igalia.com/ drivers/hv/ring_buffer.c | 16 ++++++++++++++++ drivers/video/fbdev/hyperv_fb.c | 8 +++++++- include/linux/hyperv.h | 2 ++ 3 files changed, 25 insertions(+), 1 deletion(-) diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 59a4aa86d1f3..9ceb3a7e8d19 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -280,6 +280,22 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info) ring_info->pkt_buffer_size = 0; } +/* + * Check if the ring buffer spinlock is available to take or not; used on + * atomic contexts, like panic path (see the Hyper-V framebuffer driver). + */ + +bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel) +{ + struct hv_ring_buffer_info *rinfo = &channel->outbound; + + if (spin_is_locked(&rinfo->ring_lock)) + return true; + + return false; +} +EXPORT_SYMBOL_GPL(hv_ringbuffer_spinlock_busy); + /* Write to the ring buffer. */ int hv_ringbuffer_write(struct vmbus_channel *channel, const struct kvec *kv_list, u32 kv_count, diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c index 886c564787f1..e1b65a01fb96 100644 --- a/drivers/video/fbdev/hyperv_fb.c +++ b/drivers/video/fbdev/hyperv_fb.c @@ -783,12 +783,18 @@ static void hvfb_ondemand_refresh_throttle(struct hvfb_par *par, static int hvfb_on_panic(struct notifier_block *nb, unsigned long e, void *p) { + struct hv_device *hdev; struct hvfb_par *par; struct fb_info *info; par = container_of(nb, struct hvfb_par, hvfb_panic_nb); - par->synchronous_fb = true; info = par->info; + hdev = device_to_hv_device(info->device); + + if (hv_ringbuffer_spinlock_busy(hdev->channel)) + return NOTIFY_DONE; + + par->synchronous_fb = true; if (par->need_docopy) hvfb_docopy(par, 0, dio_fb_size); synthvid_update(info, 0, 0, INT_MAX, INT_MAX); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 3b42264333ef..646f1da9f27e 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1341,6 +1341,8 @@ struct hv_ring_buffer_debug_info { int hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info, struct hv_ring_buffer_debug_info *debug_info); +bool hv_ringbuffer_spinlock_busy(struct vmbus_channel *channel); + /* Vmbus interface */ #define vmbus_driver_register(driver) \ __vmbus_driver_register(driver, THIS_MODULE, KBUILD_MODNAME) -- 2.37.1
Powered by blists - more mailing lists