RHBA-2012:0952 - Bug Fix Advisory

Topic

Updated ksh packages that fix multiple bugs are now available for Red Hat
Enterprise Linux 6.

Description

KSH-93 is the most recent version of the KornShell by David Korn of AT&T Bell
Laboratories. KornShell is a shell programming language which is also compatible
with sh, the original Bourne Shell.

This update fixes the following bugs:

• Previously, ksh sometimes did not restore terminal settings after read timeout

when operating in a multibyte environment. This could cause the terminal to no
longer echo input characters. This updates applies a patch ensuring that the
terminal is restored properly after the timeout and the user's input is now
echoed as expected. (BZ#577223)

• When exiting a subshell after a command substitution, ksh could prematurely

exit without any error message. With this update, ksh no longer terminates under
these circumstances and all subsequent commands are processed correctly.
(BZ#742930)

• Previously, ksh did not prevent modifications of variables of the read-only

type. As a consequence, ksh terminated unexpectedly with a segmentation fault
when such a variable was modified. With this update, modification of read-only
variables are not allowed, and ksh prints an error message in this scenario.
(BZ#743840)

• Previously, ksh did not close certain file descriptors prior to execution.

This could lead to a file descriptor leak, and certain applications could
consequently report error messages. With this update, file descriptors are
marked to be closed on execution if appropriate, so file descriptor leaks no
longer occur. (BZ#781498)

• In certain cases, ksh unnecessarily called the vfork() function. An extra

process was created, and it could be difficult to determine how many instances
of a script were running. A patch has been applied to address this problem, and
extra processes are no longer created if not required. (BZ#781976)

• Previously, ksh could incorrectly seek in the input stream. This could lead to

data corruption in the here-document section of a script. This update corrects
the seek behavior, so the data no longer gets corrupted in this scenario.
(BZ#786787)

• Previously, ksh did not allocate the correct amount of memory for its data

structures containing information about file descriptors. When running a task
that used file descriptors extensively, ksh terminated unexpectedly with a
segmentation fault. With this update, the proper amount of memory is allocated,
and ksh no longer crashes if file descriptors are used extensively. (BZ#798868)

• Previously, ksh did not expand the tilde (~) character properly. For example,

characters in the tilde prefix were not treated as a login name but as a part of
the path and the "No such file or directory" message was displayed. The
underlying source code has been modified and tilde expansion now works as
expected in such a scenario. (BZ#800684)

All users of ksh are advised to upgrade to these updated packages, which fix
these bugs.

Solution

Before applying this update, make sure all previously-released errata relevant
to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the Red
Hat Network to apply this update are available at
https://access.redhat.com/knowledge/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 x86_64
• Red Hat Enterprise Linux Server from RHUI 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 743840 - ksh segfaults on oop code
• BZ - 781498 - ksh shell forking during variable assignment fails to close the file descriptors in the child process prior to exec

CVEs

(none)

References

(none)