Proposal: fs/iso9660: Prevent skipping CE or ST at start of continuation area

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

i believe that the problem about CE entries sitting at the start of a SUSP
continuation area could be quite easily solved after patch [2/4] was applied,
which changes the for-loop to a while loop with the entry-advance step at its
end.

So i propose to Lidong Chen to handle this problem by another patch in
the series, which comes after [2/4] (then [2/5]).
Please verify that my thoughts about CE (and additionally about ST) are
correct and consider the following diff, which compiles but is not tested
otherwise.

I agree in advance to changing my "Signed-off-by:" to "Suggested-by:" if
deemed appropriate.

------------------------------------------------------------------------

fs/iso9660: Prevent skipping CE or ST at start of continuation area

If processing of a SUSP CE entry leads to a continuation area which begins
by entry CE or ST, then these entries were skipped without interpretation.
In case of CE this would lead to premature end of processing the SUSP entries
of the file.
In case of ST this could cause following non-SUSP bytes to be interpreted
as SUSP entries.

Signed-off-by: Thomas Schmitt <scdbackup@gmx.net>

--- grub-core/fs/iso9660.c.lidong_chen_patch_2	2022-12-15 11:46:50.654295924 +0100
+++ grub-core/fs/iso9660.c.lidong_chen_patch_2_ce_fix	2022-12-16 10:05:52.990599283 +0100
@@ -336,6 +336,12 @@ grub_iso9660_susp_iterate (grub_fshelp_n
 	    }

 	  entry = (struct grub_iso9660_susp_entry *) sua;
+
+	  if (grub_strncmp ((char *) entry->sig, "CE", 2) == 0
+	      || grub_strncmp ((char *) entry->sig, "ST", 2) == 0)
+	      /* The hook function will not process CE or ST.
+		 Advancing to the next entry would skip them. */
+	      continue;
 	}

       if (hook (entry, hook_arg))

------------------------------------------------------------------------


Have a nice day :)

Thomas