Date: Mon, 03 Jul 2017 15:35:21 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-scsi@FreeBSD.org Subject: [Bug 219701] crash in camperiphfree() Message-ID: <bug-219701-5312-i1phSKzK9s@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-219701-5312@https.bugs.freebsd.org/bugzilla/> References: <bug-219701-5312@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D219701 --- Comment #8 from commit-hook@freebsd.org --- A commit references this bug: Author: ken Date: Mon Jul 3 15:34:21 UTC 2017 New revision: 320602 URL: https://svnweb.freebsd.org/changeset/base/320602 Log: MFC r320421: ------------------------------------------------------------------------ r320421 | ken | 2017-06-27 13:26:02 -0600 (Tue, 27 Jun 2017) | 37 lines Fix a panic in camperiphfree(). If a peripheral driver (e.g. da, sa, cd) is added or removed from the peripheral driver list while an unrelated peripheral driver instance (e= .g. da0, sa5, cd2) is going away and is inside camperiphfree(), we could dereference an invalid pointer. When peripheral drivers are added or removed (see periphdriver_register= () and periphdriver_unregister()), the peripheral driver array is resized and existing entries are moved. Although we hold the topology lock while we traverse the peripheral dri= ver list, we retain a pointer to the location of the peripheral driver poin= ter and then drop the topology lock. So we are still vulnerable to the list getting moved around while the lock is dropped. To solve the problem, cache a copy of the peripheral driver pointer. If its storage location in the list changes while we have the lock dropped= , it won't have any effect. This doesn't solve the issue that peripheral drivers ("da", "cd", as opposed to individual instances like "da0", "cd0") are not generally part of a reference counting scheme to guard against deregistering them while the= re are instances active. The caller (generally the person unloading a mod= ule) has to be aware of active drivers and not unload something that is in u= se. sys/cam/cam_periph.c: In camperiphfree(), cache a pointer to the peripheral driver instance to avoid holding a pointer to an invalid memory location in the event that the peripheral driver list changes while we have the topology lock dropped. PR: kern/219701 Submitted by: avg Sponsored by: Spectra Logic ------------------------------------------------------------------------ PR: kern/219701 Sponsored by: Spectra Logic Changes: _U stable/11/ stable/11/sys/cam/cam_periph.c --=20 You are receiving this mail because: You are on the CC list for the bug.=
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