From nobody Sun Feb 8 15:54:11 2026 Received: from smtp-fw-6002.amazon.com (smtp-fw-6002.amazon.com [52.95.49.90]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8F64018643; Sat, 2 Mar 2024 16:04:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=52.95.49.90 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709395449; cv=none; b=pbobeLKStm0MXITGGPGK4PuWFo/bw6fy2h9OHMAoLFi9bRqT1HT6pvSILyvPKEE2ejG3wHmx71R+ionimFF2uvxfl3lI5RaRxvvpUNXwrVqVZxcaFfmxC/vFz8qwwdRcYIExf18FM9HmVczK233csAborKV+S3pCEpppK+0ANAQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1709395449; c=relaxed/simple; bh=SSAIn69p5KpTG+RYl5QK1udwW78txD+OXl89A4YdAuU=; h=Date:From:To:CC:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition; b=ospJ391aFc3d4RIaaRDr6NVia9blaIW4d4DdQ9cB1oJtKLNoyx/J8xHPjYpjULd6ABDGlpUxsEbN0HWFEM1s9acHGVczQ0AKYhu0JtBzwGokFWhk4bU6j8HzNNBjxFvtNJUf8mchmVqMD+xH8hkX2BaCn5HMXwx6+JwkF9vemgk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com; spf=pass smtp.mailfrom=amazon.com; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b=LAI2ESLh; arc=none smtp.client-ip=52.95.49.90 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.com header.i=@amazon.com header.b="LAI2ESLh" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1709395448; x=1740931448; h=date:from:to:cc:subject:message-id:mime-version; bh=mKU44kf1szj1NAugNFe0lwWcoXGVyPwTuTIS+BKG33o=; b=LAI2ESLhMMbWJLwGg3HWDgUm1iFnEgBd9D+18YkhEF7tUuQ7SCXvo86h LrAalFFxhDk9vyn65CKiHCkb34nuAobd35fxVJL8+MlmWT9UV/0LrG0v2 4d8U++ZTjL/MPuJODiFldj/7eGxwzXuSRQJX6fA4DTN3IWk/lzGFJHtxP A=; X-IronPort-AV: E=Sophos;i="6.06,199,1705363200"; d="scan'208";a="390492001" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO smtpout.prod.us-east-1.prod.farcaster.email.amazon.dev) ([10.43.8.6]) by smtp-border-fw-6002.iad6.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Mar 2024 16:04:06 +0000 Received: from EX19MTAEUA001.ant.amazon.com [10.0.17.79:9101] by smtpin.naws.eu-west-1.prod.farcaster.email.amazon.dev [10.0.23.38:2525] with esmtp (Farcaster) id 85a662c0-eb29-49e0-86cf-fb7cf493641c; Sat, 2 Mar 2024 16:04:04 +0000 (UTC) X-Farcaster-Flow-ID: 85a662c0-eb29-49e0-86cf-fb7cf493641c Received: from EX19D026EUB004.ant.amazon.com (10.252.61.64) by EX19MTAEUA001.ant.amazon.com (10.252.50.223) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.28; Sat, 2 Mar 2024 16:04:03 +0000 Received: from uc3ecf78c6baf56.ant.amazon.com (10.187.170.62) by EX19D026EUB004.ant.amazon.com (10.252.61.64) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1258.28; Sat, 2 Mar 2024 16:04:00 +0000 Date: Sat, 2 Mar 2024 08:03:57 -0800 From: Andrew Panyakin To: CC: , , , , , , , , , , , , , Subject: [PATCH 5.10] xen/events: close evtchn after mapping cleanup Message-ID: <20240302160357.GA2232656@uc3ecf78c6baf56.ant.amazon.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline X-ClientProxiedBy: EX19D045UWA003.ant.amazon.com (10.13.139.46) To EX19D026EUB004.ant.amazon.com (10.252.61.64) Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Maximilian Heyne Commit fa765c4b4aed2d64266b694520ecb025c862c5a9 upstream shutdown_pirq and startup_pirq are not taking the irq_mapping_update_lock because they can't due to lock inversion. Both are called with the irq_desc->lock being taking. The lock order, however, is first irq_mapping_update_lock and then irq_desc->lock. This opens multiple races: - shutdown_pirq can be interrupted by a function that allocates an event channel: CPU0 CPU1 shutdown_pirq { xen_evtchn_close(e) __startup_pirq { EVTCHNOP_bind_pirq -> returns just freed evtchn e set_evtchn_to_irq(e, irq) } xen_irq_info_cleanup() { set_evtchn_to_irq(e, -1) } } Assume here event channel e refers here to the same event channel number. After this race the evtchn_to_irq mapping for e is invalid (-1). - __startup_pirq races with __unbind_from_irq in a similar way. Because __startup_pirq doesn't take irq_mapping_update_lock it can grab the evtchn that __unbind_from_irq is currently freeing and cleaning up. In this case even though the event channel is allocated, its mapping can be unset in evtchn_to_irq. The fix is to first cleanup the mappings and then close the event channel. In this way, when an event channel gets allocated it's potential previous evtchn_to_irq mappings are guaranteed to be unset alread= y. This is also the reverse order of the allocation where first the event channel is allocated and then the mappings are setup. On a 5.10 kernel prior to commit 3fcdaf3d7634 ("xen/events: modify internal [un]bind interfaces"), we hit a BUG like the following during probing of NV= Me devices. The issue is that during nvme_setup_io_queues, pci_free_irq is called for every device which results in a call to shutdown_pirq. With many nvme devices it's therefore likely to hit this race during boot because there will be multiple calls to shutdown_pirq and startup_pirq are running potentially in parallel. ------------[ cut here ]------------ blkfront: xvda: barrier or flush: disabled; persistent grants: enabled; i= ndirect descriptors: enabled; bounce buffer: enabled kernel BUG at drivers/xen/events/events_base.c:499! invalid opcode: 0000 [#1] SMP PTI CPU: 44 PID: 375 Comm: kworker/u257:23 Not tainted 5.10.201-191.748.amzn2= .x86_64 #1 Hardware name: Xen HVM domU, BIOS 4.11.amazon 08/24/2006 Workqueue: nvme-reset-wq nvme_reset_work RIP: 0010:bind_evtchn_to_cpu+0xdf/0xf0 Code: 5d 41 5e c3 cc cc cc cc 44 89 f7 e8 2b 55 ad ff 49 89 c5 48 85 c0 0= f 84 64 ff ff ff 4c 8b 68 30 41 83 fe ff 0f 85 60 ff ff ff <0f> 0b 66 66 2e= 0f 1f 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 RSP: 0000:ffffc9000d533b08 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000006 RDX: 0000000000000028 RSI: 00000000ffffffff RDI: 00000000ffffffff RBP: ffff888107419680 R08: 0000000000000000 R09: ffffffff82d72b00 R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000001ed R13: 0000000000000000 R14: 00000000ffffffff R15: 0000000000000002 FS: 0000000000000000(0000) GS:ffff88bc8b500000(0000) knlGS:0000000000000= 000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000000 CR3: 0000000002610001 CR4: 00000000001706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? show_trace_log_lvl+0x1c1/0x2d9 ? show_trace_log_lvl+0x1c1/0x2d9 ? set_affinity_irq+0xdc/0x1c0 ? __die_body.cold+0x8/0xd ? die+0x2b/0x50 ? do_trap+0x90/0x110 ? bind_evtchn_to_cpu+0xdf/0xf0 ? do_error_trap+0x65/0x80 ? bind_evtchn_to_cpu+0xdf/0xf0 ? exc_invalid_op+0x4e/0x70 ? bind_evtchn_to_cpu+0xdf/0xf0 ? asm_exc_invalid_op+0x12/0x20 ? bind_evtchn_to_cpu+0xdf/0xf0 ? bind_evtchn_to_cpu+0xc5/0xf0 set_affinity_irq+0xdc/0x1c0 irq_do_set_affinity+0x1d7/0x1f0 irq_setup_affinity+0xd6/0x1a0 irq_startup+0x8a/0xf0 __setup_irq+0x639/0x6d0 ? nvme_suspend+0x150/0x150 request_threaded_irq+0x10c/0x180 ? nvme_suspend+0x150/0x150 pci_request_irq+0xa8/0xf0 ? __blk_mq_free_request+0x74/0xa0 queue_request_irq+0x6f/0x80 nvme_create_queue+0x1af/0x200 nvme_create_io_queues+0xbd/0xf0 nvme_setup_io_queues+0x246/0x320 ? nvme_irq_check+0x30/0x30 nvme_reset_work+0x1c8/0x400 process_one_work+0x1b0/0x350 worker_thread+0x49/0x310 ? process_one_work+0x350/0x350 kthread+0x11b/0x140 ? __kthread_bind_mask+0x60/0x60 ret_from_fork+0x22/0x30 Modules linked in: ---[ end trace a11715de1eee1873 ]--- Fixes: d46a78b05c0e ("xen: implement pirq type event channels") Cc: stable@vger.kernel.org Co-debugged-by: Andrew Panyakin Signed-off-by: Maximilian Heyne [apanyaki: backport to v5.10-stable] Signed-off-by: Andrew Paniakin --- Compare to upstream patch this one does not have close_evtchn flag because there is no need to handle static event channels. This feature was added only in 58f6259b7a08f ("xen/evtchn: Introduce new IOCTL to bind static evtchn") drivers/xen/events/events_base.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_b= ase.c index 24e39984914f..f608663bdfd5 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -885,8 +885,8 @@ static void shutdown_pirq(struct irq_data *data) return; =20 do_mask(info, EVT_MASK_REASON_EXPLICIT); - xen_evtchn_close(evtchn); xen_irq_info_cleanup(info); + xen_evtchn_close(evtchn); } =20 static void enable_pirq(struct irq_data *data) @@ -929,8 +929,6 @@ static void __unbind_from_irq(unsigned int irq) if (VALID_EVTCHN(evtchn)) { unsigned int cpu =3D cpu_from_irq(irq); =20 - xen_evtchn_close(evtchn); - switch (type_from_irq(irq)) { case IRQT_VIRQ: per_cpu(virq_to_irq, cpu)[virq_from_irq(irq)] =3D -1; @@ -943,6 +941,7 @@ static void __unbind_from_irq(unsigned int irq) } =20 xen_irq_info_cleanup(info); + xen_evtchn_close(evtchn); } =20 xen_free_irq(irq); --=20 2.40.1