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dmu_objset_userquota_get_ids uses dn_bonus unsafely 

The function dmu_objset_userquota_get_ids() checks and uses dn->dn_bonus
outside of dn_struct_rwlock. If the dnode is being freed then the bonus
dbuf may be in the process of getting evicted. In this case there is a
race that may cause dmu_objset_userquota_get_ids() to access the dbuf
after it has been destroyed. To prevent this, ensure that when we are
using the bonus dbuf we are either holding a reference on it or have
taken dn_struct_rwlock.

Signed-off-by: Ned Bass <bass6@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3443
This commit is contained in:
Ned Bass 2015-05-28 16:14:19 -07:00 committed by Brian Behlendorf
parent d617648c7f
commit 5f8e1e8505
1 changed files with 17 additions and 3 deletions
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18
module/zfs/dmu_objset.c
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@ -1314,6 +1314,7 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
int flags = dn->dn_id_flags;
int error;
boolean_t have_spill = B_FALSE;
boolean_t have_bonus = B_FALSE;
if (!dmu_objset_userused_enabled(dn->dn_objset))
return;
@ -1325,8 +1326,21 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
if (before && dn->dn_bonuslen != 0)
data = DN_BONUS(dn->dn_phys);
else if (!before && dn->dn_bonuslen != 0) {
if (dn->dn_bonus) {
db = dn->dn_bonus;
if (db != NULL) {
if (!RW_WRITE_HELD(&dn->dn_struct_rwlock)) {
have_bonus = dbuf_try_add_ref((dmu_buf_t *)db,
dn->dn_objset, dn->dn_object,
DMU_BONUS_BLKID, FTAG);
/*
* The hold will fail if the buffer is
* being evicted due to unlink, in which
* case nothing needs to be done.
*/
if (!have_bonus)
return;
}
mutex_enter(&db->db_mtx);
data = dmu_objset_userquota_find_data(db, tx);
} else {
@ -1401,7 +1415,7 @@ dmu_objset_userquota_get_ids(dnode_t *dn, boolean_t before, dmu_tx_t *tx)
dn->dn_id_flags |= DN_ID_CHKED_BONUS;
}
mutex_exit(&dn->dn_mtx);
if (have_spill)
if (have_spill || have_bonus)
dmu_buf_rele((dmu_buf_t *)db, FTAG);
}