linux-kernel - [PATCH] kgdb/kdb: A fix for kdb command table expansion

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Date:	Mon, 10 Dec 2012 15:37:22 -0600
From:	John Blackwood <john.blackwood@...r.com>
To:	<linux-kernel@...r.kernel.org>
CC:	Jason Wessel <jason.wessel@...driver.com>
Subject: [PATCH] kgdb/kdb: A fix for kdb command table expansion

When locally adding in some additional kdb commands, I stumbled
across an issue with the dynamic expansion of the kdb command table.
When the number of kdb commands exceeds the size of the statically
allocated kdb_base_commands[] array, additional space is allocated in
the kdb_register_repeat() routine.

The unused portion of the newly allocated array was not being initialized
to zero properly and this would result in segfaults when help '?' was
executed or when a search for a non-existing command would traverse the
command table beyond the end of valid command entries and then attempt
to use the non-zeroed area as actual command entries.

Signed-off-by: John Blackwood <john.blackwood@...r.com>
Index: b/kernel/debug/kdb/kdb_main.c
===================================================================
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -3341,7 +3341,7 @@ int kdb_register_repeat(char *cmd,
  			  (kdb_max_commands - KDB_BASE_CMD_MAX) * sizeof(*new));
  			kfree(kdb_commands);
  		}
-		memset(new + kdb_max_commands, 0,
+		memset(new + kdb_max_commands - KDB_BASE_CMD_MAX, 0,
  		       kdb_command_extend * sizeof(*new));
  		kdb_commands = new;
  		kp = kdb_commands + kdb_max_commands - KDB_BASE_CMD_MAX;
--
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