Date: Tue, 27 Jun 2017 19:26:48 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-scsi@FreeBSD.org Subject: [Bug 219701] crash in camperiphfree() Message-ID: <bug-219701-5312-Lm1tJblatS@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 #4 from commit-hook@freebsd.org --- A commit references this bug: Author: ken Date: Tue Jun 27 19:26:03 UTC 2017 New revision: 320421 URL: https://svnweb.freebsd.org/changeset/base/320421 Log: 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 driver list, we retain a pointer to the location of the peripheral driver pointer 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 oppo= sed to individual instances like "da0", "cd0") are not generally part of a reference counting scheme to guard against deregistering them while there are instances active. The caller (generally the person unloading a modul= e) has to be aware of active drivers and not unload something that is in use. 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 MFC after: 3 days Sponsored by: Spectra Logic Changes: head/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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