Date: Tue, 11 May 2021 04:30:19 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: 12288bd999ca - main - cache: fix lockless absolute symlink traversal to non-fp mounts Message-ID: <202105110430.14B4UJxA003819@gitrepo.freebsd.org>
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The branch main has been updated by mjg: URL: https://cgit.FreeBSD.org/src/commit/?id=12288bd999ca3a493b8dc4cba109e5a8fa838c45 commit 12288bd999ca3a493b8dc4cba109e5a8fa838c45 Author: Mateusz Guzik <mjg@FreeBSD.org> AuthorDate: 2021-05-11 03:48:08 +0000 Commit: Mateusz Guzik <mjg@FreeBSD.org> CommitDate: 2021-05-11 04:30:12 +0000 cache: fix lockless absolute symlink traversal to non-fp mounts Said lookups would incorrectly fail with EOPNOTSUP. Reported by: kib --- sys/kern/vfs_cache.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c index 607b1e67a40a..5b978511db17 100644 --- a/sys/kern/vfs_cache.c +++ b/sys/kern/vfs_cache.c @@ -3904,6 +3904,7 @@ struct cache_fpl { #endif }; +static bool cache_fplookup_mp_supported(struct mount *mp); static bool cache_fplookup_is_mp(struct cache_fpl *fpl); static int cache_fplookup_cross_mount(struct cache_fpl *fpl); static int cache_fplookup_partial_setup(struct cache_fpl *fpl); @@ -5142,6 +5143,19 @@ cache_fplookup_symlink(struct cache_fpl *fpl) if (seqc_in_modify(fpl->dvp_seqc)) { return (cache_fpl_aborted(fpl)); } + /* + * The main loop assumes that ->dvp points to a vnode belonging + * to a filesystem which can do lockless lookup, but the absolute + * symlink can be wandering off to one which does not. + */ + mp = atomic_load_ptr(&fpl->dvp->v_mount); + if (__predict_false(mp == NULL)) { + return (cache_fpl_aborted(fpl)); + } + if (!cache_fplookup_mp_supported(mp)) { + cache_fpl_checkpoint(fpl); + return (cache_fpl_partial(fpl)); + } } return (0); }
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