Date: Thu, 5 Oct 2023 12:44:50 GMT From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: cd2105d691f4 - main - vfs cache: denote a known bug in cache_remove_cnp Message-ID: <202310051244.395CioXl027458@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=cd2105d691f446f7dbddf5965d82b9e9103bc8d2 commit cd2105d691f446f7dbddf5965d82b9e9103bc8d2 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2023-10-05 12:32:29 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2023-10-05 12:44:43 +0000 vfs cache: denote a known bug in cache_remove_cnp --- sys/kern/vfs_cache.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 560ff7d441c0..cc2f405d5281 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -1822,6 +1822,15 @@ retry_dotdot: return (1); } + /* + * XXX note that access here is completely unlocked with no provisions + * to keep the hash allocated. If one is sufficiently unlucky a + * parallel cache resize can reallocate the hash, unmap backing pages + * and cause the empty check below to fault. + * + * Fixing this has epsilon priority, but can be done with no overhead + * for this codepath with sufficient effort. + */ hash = cache_get_hash(cnp->cn_nameptr, cnp->cn_namelen, dvp); blp = HASH2BUCKETLOCK(hash); retry:
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