Date: Thu, 10 Aug 2023 17:33:44 GMT From: Kyle Evans <kevans@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 2bd446d7f1a0 - main - kern: osd: avoid dereferencing freed slots Message-ID: <202308101733.37AHXiJH042981@gitrepo.freebsd.org>
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The branch main has been updated by kevans: URL: https://cgit.FreeBSD.org/src/commit/?id=2bd446d7f1a03fbf6d98ace4548f8793599f48fb commit 2bd446d7f1a03fbf6d98ace4548f8793599f48fb Author: Kyle Evans <kevans@FreeBSD.org> AuthorDate: 2023-08-10 17:32:33 +0000 Commit: Kyle Evans <kevans@FreeBSD.org> CommitDate: 2023-08-10 17:33:26 +0000 kern: osd: avoid dereferencing freed slots If a slot is freed that isn't the last one, we'll set its destructor to NULL to indicate that it's been freed and leave a hole in the slot map. Check osd_destructors in osd_call() to avoid dereferencing a method that is potentially from a module that's been unloaded. This scenario would most commonly surface when two modules are loaded that osd_register(), then the earlier one deregisters and an osd_call() is made after the fact. In the specific report that triggered the investigation, kldload if_wg -> kldload linux* -> kldunload if_wg -> destroy a jail -> panic. Noted in the review, but left for follow-up work, is that the realloc that may happen in osd_deregister() should likely go away and the assumption that reallocating to a smaller size cannot fail is actually not correct. Reported by: dim Reviewed by: markj, jamie Differential Revision: https://reviews.freebsd.org/D41404 --- sys/kern/kern_osd.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/sys/kern/kern_osd.c b/sys/kern/kern_osd.c index 23178731b899..ced6df31cf44 100644 --- a/sys/kern/kern_osd.c +++ b/sys/kern/kern_osd.c @@ -396,6 +396,9 @@ osd_call(u_int type, u_int method, void *obj, void *data) error = 0; sx_slock(&osdm[type].osd_module_lock); for (i = 0; i < osdm[type].osd_ntslots; i++) { + /* Hole in the slot map; avoid dereferencing. */ + if (osdm[type].osd_destructors[i] == NULL) + continue; methodfun = osdm[type].osd_methods[i * osdm[type].osd_nmethods + method]; if (methodfun != NULL && (error = methodfun(obj, data)) != 0)
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