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cache: fix lockless absolute symlink traversal to non-fp mounts

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Said lookups would incorrectly fail with EOPNOTSUP.

Reported by:	kib
This commit is contained in:
Mateusz Guzik 2021-05-11 05:48:08 +02:00
parent a436e66531
commit 12288bd999
1 changed files with 14 additions and 0 deletions
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14
sys/kern/vfs_cache.c
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@ -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);
}