Hi, On Mon, Apr 28, 2014 at 09:27:58AM +0200, Axel Beckert wrote: > On Sun, Apr 27, 2014 at 09:58:51PM -0700, Maciej Żenczykowski wrote: > > Curious I just reinstalled bash on my fedora 20 x86_64 system. > > > > $ uname -a > > Linux eonwe.lan 3.13.10-200.1mz.fc20.x86_64 #1 SMP Sat Apr 26 01:19:02 > > PDT 2014 x86_64 x86_64 x86_64 GNU/Linux > > > > $ ls -al /proc/$$/exe > > lrwxrwxrwx. 1 maze maze 0 Apr 27 21:48 /proc/10848/exe -> > > /usr/bin/bash (deleted) > > > > $ /proc/$$/exe --version > > GNU bash, version 4.2.47(1)-release (x86_64-redhat-linux-gnu) > [...] > > And as you can see I can still run the old marked deleted binary. > > Hrm, interesting. > > > Maybe the problem is zsh? > > Sounds likely. Will test later. Thanks for the feedback and idea!
Nope. With bash: 1/0/0 root@nemo2:pts/11 13:01:32 [~] # /proc/8052/exe -ls bash: /proc/8052/exe: Permission denied 2/126/0 root@nemo2:pts/11 13:02:00 [~] # ls -l /proc/8052/exe lrwxrwxrwx 1 root root 0 Apr 28 04:50 /proc/8052/exe -> /usr/bin/screen (deleted) 3/0/0 root@nemo2:pts/11 13:02:04 [~] # I suspect it's rather related to screen being installed setuid. Let's test with bash as the binary which is replaced: 3/0/0 root@nemo2:pts/11 13:02:04 [~] # apt-get install --reinstall bash Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 1 not upgraded. Need to get 1.138 kB of archives. After this operation, 0 B of additional disk space will be used. Get:1 http://debian.ethz.ch/debian/ sid/main bash i386 4.3-7 [1.138 kB] Fetched 1.138 kB in 0s (4.597 kB/s) (Reading database ... 554999 files and directories currently installed.) Preparing to unpack .../archives/bash_4.3-7_i386.deb ... Unpacking bash (4.3-7) over (4.3-7) ... Processing triggers for menu (2.1.46) ... Processing triggers for install-info (5.2.0.dfsg.1-2) ... Processing triggers for man-db (2.6.7.1-1) ... Setting up bash (4.3-7) ... update-alternatives: using /usr/share/man/man7/bash-builtins.7.gz to provide /usr/share/man/man7/builtins.7.gz (builtins.7.gz) in auto mode Processing triggers for menu (2.1.46) ... 4/0/0 root@nemo2:pts/11 14:23:18 [~] # ls -l /proc/$$/exe lrwxrwxrwx 1 root root 0 Apr 28 14:21 /proc/18737/exe -> /bin/bash (deleted) 5/0/0 root@nemo2:pts/11 14:23:50 [~] # !$ /proc/$$/exe 1/0/0 root@nemo2:pts/11 14:23:58 [~] # exit exit 6/0/0 root@nemo2:pts/11 14:24:08 [~] # So it works with bash, but not screen. Which makes me even more confident that this trick doesn't work for setuid binaries and hence not for screen on Debian. *sigh* Kind regards, Axel -- /~\ Plain Text Ribbon Campaign | Axel Beckert \ / Say No to HTML in E-Mail and News | a...@deuxchevaux.org (Mail) X See http://www.nonhtmlmail.org/campaign.html | a...@noone.org (Mail+Jabber) / \ I love long mails: http://email.is-not-s.ms/ | http://noone.org/abe/ (Web)
