Patchwork [4/5] readline: Fix buffer overrun on re-add to history

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Submitter Stefan Hajnoczi
Date Nov. 7, 2011, 9:26 a.m.
Message ID <1320658020-4374-5-git-send-email-stefanha@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/124022/
State New
Headers show

Comments

Stefan Hajnoczi - Nov. 7, 2011, 9:26 a.m.
From: Markus Armbruster <armbru@redhat.com>

readline_hist_add() moves the history entry to the end of history.  It
uses memmove() to move rs->history[idx + 1..] to rs->history[idx..].
However, its size argument is off by two array elements, so it writes
one element beyond rs->history[], and reads two.

On my system, this clobbers rs->hist_entry and the hole right after
it.  Since the function assigns to rs->hist_entry in time, the bug has
no ill effects for me.

Spotted by Coverity.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 readline.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

Patch

diff --git a/readline.c b/readline.c
index 6a3160a..a6c0039 100644
--- a/readline.c
+++ b/readline.c
@@ -236,7 +236,7 @@  static void readline_hist_add(ReadLineState *rs, const char *cmdline)
 	    new_entry = hist_entry;
 	    /* Put this entry at the end of history */
 	    memmove(&rs->history[idx], &rs->history[idx + 1],
-		    (READLINE_MAX_CMDS - idx + 1) * sizeof(char *));
+		    (READLINE_MAX_CMDS - (idx + 1)) * sizeof(char *));
 	    rs->history[READLINE_MAX_CMDS - 1] = NULL;
 	    for (; idx < READLINE_MAX_CMDS; idx++) {
 		if (rs->history[idx] == NULL)