From 9a9da2c299a0adcd36b4efd1b1c0ee2883beba7b Mon Sep 17 00:00:00 2001 From: Johnothan King Date: Mon, 6 Jul 2020 13:51:44 -0700 Subject: [PATCH] Fix use of strdup on a NULL pointer (#63) The following set of commands can rarely cause a memory fault when auditing[*] is enabled, although most of the time it will simply cause ksh to write '(null)' to the auditing file in place of a tty name: $ [ -e /etc/ksh_audit ] || echo "/tmp/ksh_auditfile;$(id -u)" | sudo tee /etc/ksh_audit; $ v=$(ksh 2> /dev/null +o rc -ic $'getopts a:bc: opt --man\nprint $?') $ cat /tmp/ksh_auditfile 1000;1593599493;(null); getopts a:bc: opt --man This happens because strdup is used unconditionally on the pointer returned by 'ttyname', which can be NULL if stderr is closed. This then causes 'hp->tty' to be set to null, as strdup returns NULL. See https://github.com/att/ast/issues/1028 src/cmd/ksh93/edit/history.c: - Make strdup duplicate 'notty' instead of NULL to prevent crashes. [*] https://blog.fpmurphy.com/2008/12/ksh93-auditing-and-accounting.html Cherry-picked-by: Lukáš Zaoral Upstream-commit: 9a9da2c299a0adcd36b4efd1b1c0ee2883beba7b --- src/cmd/ksh93/edit/history.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/src/cmd/ksh93/edit/history.c b/src/cmd/ksh93/edit/history.c index d6737e209ca0..f40f27b4a4d7 100644 --- a/src/cmd/ksh93/edit/history.c +++ b/src/cmd/ksh93/edit/history.c @@ -395,7 +395,7 @@ int sh_histinit(void *sh_context) if(fd>=0) { fcntl(fd,F_SETFD,FD_CLOEXEC); - hp->tty = strdup(ttyname(2)); + hp->tty = strdup(isatty(2)?ttyname(2):"notty"); hp->auditfp = sfnew((Sfio_t*)0,NULL,-1,fd,SF_WRITE); } }