Date: Fri, 1 Mar 2019 01:18:40 +0000 (UTC) From: Marcin Wojtas <mw@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r344676 - head/sys/kern Message-ID: <201903010118.x211IeVj027670@repo.freebsd.org>
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Author: mw Date: Fri Mar 1 01:18:39 2019 New Revision: 344676 URL: https://svnweb.freebsd.org/changeset/base/344676 Log: Prevent detaching driver if the attach is not finished When the device is in attaching state, detach should return EBUSY instead of success. In other case, there could be race between attach and detach during the driver unloading. If driver goes sleep and releases GIANT lock during attaching, unloading module could start. In such case when attach continues after module unload, page fault "supervisor read instruction, page not present" occurred. This patch works around the real issue, which is a locking deficiency of the busses. Submitted by: Rafal Kozik <rk@semihalf.com> Reviewed by: imp Obtained from: Semihalf MFC after: 2 weeks Sponsored by: Amazon, Inc. Differential Revision: https://reviews.freebsd.org/D19375 Modified: head/sys/kern/subr_bus.c Modified: head/sys/kern/subr_bus.c ============================================================================== --- head/sys/kern/subr_bus.c Thu Feb 28 23:00:47 2019 (r344675) +++ head/sys/kern/subr_bus.c Fri Mar 1 01:18:39 2019 (r344676) @@ -3004,6 +3004,10 @@ device_detach(device_t dev) PDEBUG(("%s", DEVICENAME(dev))); if (dev->state == DS_BUSY) return (EBUSY); + if (dev->state == DS_ATTACHING) { + device_printf(dev, "device in attaching state! Deferring detach.\n"); + return (EBUSY); + } if (dev->state != DS_ATTACHED) return (0);
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