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[PATCH V2] xfs_repair: skip freelist scan of corrupt agf in no-modify mo

To: xfs-oss <xfs@xxxxxxxxxxx>
Subject: [PATCH V2] xfs_repair: skip freelist scan of corrupt agf in no-modify mode
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Sat, 02 Mar 2013 15:23:12 -0600
Cc: Ole Tange <tange@xxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51313DE8.5080104@xxxxxxxxxxx>
References: <51313DE8.5080104@xxxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130216 Thunderbird/17.0.3
In xfs_repair's no-modify mode (-n), verify_set_agf doesn't fix up
bad freelist blocks that it finds.  When we get to scan_freelist,
this can wreak havoc if, for example, first > last and the loop
never exits; we index agfl->agfl_bno[i] off into the weeds.

To fix this, re-check the values in no-modify mode, and if
they're off, warn about it and skip the scan.

Reported-by: Ole Tange <tange@xxxxxxxxxx>
Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>

V2: Remove dumb mistakes :/

diff --git a/repair/scan.c b/repair/scan.c
index 5345094..1d39bdc 100644
--- a/repair/scan.c
+++ b/repair/scan.c
@@ -1066,6 +1066,18 @@ scan_freelist(
        agfl = XFS_BUF_TO_AGFL(agflbuf);
+       if (no_modify) {
+               /* agf values not fixed in verify_set_agf, so recheck */
+               if (be32_to_cpu(agf->agf_flfirst) >= XFS_AGFL_SIZE(mp) ||
+                   be32_to_cpu(agf->agf_fllast) >= XFS_AGFL_SIZE(mp)) {
+                       do_warn(_("agf %d freelist blocks bad, skipping "
+                                 "freelist scan\n"), i);
+                       return;
+               }
+       } else /* should have been fixed in verify_set_agf() */
+               ASSERT(0);
        i = be32_to_cpu(agf->agf_flfirst);
        count = 0;
        for (;;) {

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