ZAP: Fix leaf references on zap_expand_leaf() errors

Depending on kind of error zap_expand_leaf() may return with or
without valid leaf reference held.  Make sure it returns NULL if
due to error it has no leaf to return.  Make its callers to check
the returned leaf pointer, and release the leaf if it is not NULL.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #12366
Closes #16159

diff --git a/module/zfs/zap.c b/module/zfs/zap.c
index 1b6b16fc66627bf52f0629feabe395b1476391c3..81dab80daf87098d9ed5703b01166a545e411689 100644 (file)
--- a/module/zfs/zap.c
+++ b/module/zfs/zap.c
@@ -711,6 +711,7 @@ zap_expand_leaf(zap_name_t *zn, zap_leaf_t *l,
                uint64_t object = zap->zap_object;
 
                zap_put_leaf(l);
+               *lp = l = NULL;
                zap_unlockdir(zap, tag);
                err = zap_lockdir(os, object, tx, RW_WRITER,
                    FALSE, FALSE, tag, &zn->zn_zap);
@@ -920,21 +921,17 @@ retry:
        } else if (err == EAGAIN) {
                err = zap_expand_leaf(zn, l, tag, tx, &l);
                zap = zn->zn_zap;       /* zap_expand_leaf() may change zap */
-               if (err == 0) {
+               if (err == 0)
                        goto retry;
-               } else if (err == ENOSPC) {
-                       /*
-                        * If we failed to expand the leaf, then bailout
-                        * as there is no point trying
-                        * zap_put_leaf_maybe_grow_ptrtbl().
-                        */
-                       return (err);
-               }
        }
 
 out:
-       if (zap != NULL)
-               zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
+       if (l != NULL) {
+               if (err == ENOSPC)
+                       zap_put_leaf(l);
+               else
+                       zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
+       }
        return (err);
 }
 
@@ -991,8 +988,12 @@ retry:
                        goto retry;
        }
 
-       if (zap != NULL)
-               zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
+       if (l != NULL) {
+               if (err == ENOSPC)
+                       zap_put_leaf(l);
+               else
+                       zap_put_leaf_maybe_grow_ptrtbl(zn, l, tag, tx);
+       }
        return (err);
 }