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[Bug 1422795] Re: bash crashes often if inputrc contains revert-all-at-newline

To: touch-packages@xxxxxxxxxxxxxxxxxxx
From: Jeffrey Hutzelman <1422795@xxxxxxxxxxxxxxxxxx>
Date: Fri, 16 Oct 2015 22:41:09 -0000
Reply-to: Bug 1422795 <1422795@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

This was fixed in 4.3-8 and so is already fixed in utopic and later. It
will require an SRU to fix in trusty. I've attached a debdiff
containing the needed change.

** Description changed:

Debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747341
The Debian bug includes complete reproduction case. Basically:
with .inputrc containing
set revert-all-at-newline On

Go back in the commandline history, edit a command, then submit a different command (may be empty)
Such as:
$ ls something
$ <UP><CTRL+W><DOWN><ENTER>

Attached diff is confirmed to fix the issue.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: bash 4.3-7ubuntu1.5 [origin: goobuntu-trusty-testing-desktop]
ProcVersionSignature: Ubuntu 3.13.0-44.73-generic 3.13.11-ckt12
Uname: Linux 3.13.0-44-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.14.1-0ubuntu3.6
Architecture: amd64
CurrentDesktop: X-Cinnamon
Date: Tue Feb 17 15:49:30 2015
SourcePackage: bash
UpgradeStatus: No upgrade log present (probably fresh install)
modified.conffile..etc.bash.bashrc: [modified]
mtime.conffile..etc.bash.bashrc: 2015-01-27T03:27:18.751405
+
+
+ [Test Case]
+
+ Adapted from the Debian bug report:
+
+ 1. echo "set revert-all-at-newline on" > bug.inputrc
+ 2. INPUTRC=bug.inputrc bash
+ 3. echo hello
+ 4. ^P^U^N^M [Hold down control and type "punm".]
+
+ Bash should die immediately with SIGABRT.
+
+
+ [Regression Potential]
+
+ Relatively low.
+
+ The change has no effect at all unless _rl_revert_all_lines() is called,
+ which only happens if revert-all-at-newline is set, and then only when a
+ newline is typed. So, the potential for regression is essentially zero for
+ non-interactive shells and for anyone not using revert-all-at-newline (which
+ is not the default).
+
+ Further, this change appeared upstream and in both Debian and Ubuntu over
+ a year ago, so it's had plenty of public testing.
+
+ lib/readline/misc.c:_rl_revert_all_lines() contains a loop which iterates
+ over history entries, reverting changes to each history entry. This patch
+ causes entry->data, which points to the per-entry undo list, to be cleared
+ before reverting edits rather than after. At first glance, this shouldn't
+ make any difference. However, it prevents rl_do_undo() from replacing the
+ history entry with one reflecting the change. Otherwise, the entry gets
+ freed, leaving _rl_revert_all_lines() with an invalid pointer.
+
+ _Not_ having an invalid pointer and double-free certainly can't be worse
+ than the current situation. Since we're avoiding is making the pointer
+ invalid rather than not doing the free, the chance of a new leak is pretty
+ much nonexistent.

** Patch added: "debdiff containing the upstream patch"
https://bugs.launchpad.net/gnubash/+bug/1422795/+attachment/4497315/+files/bash-readline-revert.debdiff

--
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https://bugs.launchpad.net/bugs/1422795

Title:
bash crashes often if inputrc contains revert-all-at-newline

Status in Gnu Bash:
New
Status in bash package in Ubuntu:
Confirmed
Status in bash package in Debian:
Unknown

Bug description:
Debian bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=747341
The Debian bug includes complete reproduction case. Basically:
with .inputrc containing
set revert-all-at-newline On

Go back in the commandline history, edit a command, then submit a different command (may be empty)
Such as:
$ ls something
$ <UP><CTRL+W><DOWN><ENTER>

Attached diff is confirmed to fix the issue.

[Test Case]

Adapted from the Debian bug report:

1. echo "set revert-all-at-newline on" > bug.inputrc
2. INPUTRC=bug.inputrc bash
3. echo hello
4. ^P^U^N^M [Hold down control and type "punm".]

Bash should die immediately with SIGABRT.

[Regression Potential]

Relatively low.

The change has no effect at all unless _rl_revert_all_lines() is called,
which only happens if revert-all-at-newline is set, and then only when a
newline is typed. So, the potential for regression is essentially zero for
non-interactive shells and for anyone not using revert-all-at-newline (which
is not the default).

Further, this change appeared upstream and in both Debian and Ubuntu over
a year ago, so it's had plenty of public testing.

lib/readline/misc.c:_rl_revert_all_lines() contains a loop which iterates
over history entries, reverting changes to each history entry. This patch
causes entry->data, which points to the per-entry undo list, to be cleared
before reverting edits rather than after. At first glance, this shouldn't
make any difference. However, it prevents rl_do_undo() from replacing the
history entry with one reflecting the change. Otherwise, the entry gets
freed, leaving _rl_revert_all_lines() with an invalid pointer.

_Not_ having an invalid pointer and double-free certainly can't be worse
than the current situation. Since we're avoiding is making the pointer
invalid rather than not doing the free, the chance of a new leak is pretty
much nonexistent.

To manage notifications about this bug go to:
https://bugs.launchpad.net/gnubash/+bug/1422795/+subscriptions

References

[Bug 1422795] [NEW] bash crashes often if inputrc contains revert-all-at-newline
From: Sven Mueller, 2015-02-17