[Bug 212168] [panic] [UFS] use-after-free panic (0xdeadc0dedeadc0de)

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212168

--- Comment #10 from Kirk McKusick <mckusick at FreeBSD.org> ---
It appears that there is an item on the worklist that has been prematurely
freed. This freeing should be impossible as anything on a worklist has its
ONWORKLIST flag set and the worklist freeing routine will panic if the
ONWORKLIST flag is set. However I have written the following check to see if we
are finding freed items on the worklist in softdep_disk_io_initiation():

Index: sys/ufs/ffs/ffs_softdep.c
===================================================================
--- sys/ufs/ffs/ffs_softdep.c   (revision 305057)
+++ sys/ufs/ffs/ffs_softdep.c   (working copy)
@@ -9949,6 +9949,13 @@

        if ((wk = LIST_FIRST(&bp->b_dep)) == NULL)
                return;
+       if (wk->wk_type > D_LAST + 1) {
+               printf("dead worklist: %p next %p prev %p type %s state
0x%X\n",
+                   wk, wk->wk_list.le_next, wk->wk_list.le_prev,
+                   TYPENAME(wk->wk_type), wk->wk_state);
+               LIST_INIT(&bp->b_dep);
+               return;
+       }
        ump = VFSTOUFS(wk->wk_mp);

        marker.wk_type = D_LAST + 1;    /* Not a normal workitem */

I would appreciate your running with this patch and reporting if you get the
"dead worklist" error message.

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