Jan Engelhardt <[email protected]> wrote:
>
> >This patch tries to fix the strange behaviour in /proc/<pid>/,
> >where it is currently possible for the owner of a process to
> >temporarily chmod the entries.
>
> I am on 2.6.13-rc3-git5 and I do not see such behavior:
>
> 08:16 spectre:/proc/21345 # chown 1337 smaps
> 08:16 spectre:/proc/21345 # l -n smaps
> -r--r--r-- 1 25121 0 0 Aug 3 08:16 smaps
> 08:16 spectre:/proc/21345 #
Did you mean "chmod"? And I don't even have "smaps".
I tried this on 2.6.13-rc5 to make sure it hasn't been fixed since
2.6.12.3. Here is a sample session to illustrate the problem:
$ uname -sr
Linux 2.6.13-rc5
$ ./a.out &
[2] 181
$ cd /proc/181
$ ls -l
total 0
-r-------- 1 jpv user 0 Aug 3 11:37 auxv
-r--r--r-- 1 jpv user 0 Aug 3 11:37 cmdline
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 cwd -> ...
-r-------- 1 jpv user 0 Aug 3 11:37 environ
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 exe -> ...
dr-x------ 2 jpv user 0 Aug 3 11:37 fd
-r--r--r-- 1 jpv user 0 Aug 3 11:37 maps
-rw------- 1 jpv user 0 Aug 3 11:37 mem
-r--r--r-- 1 jpv user 0 Aug 3 11:37 mounts
-rw-r--r-- 1 jpv user 0 Aug 3 11:37 oom_adj
-r--r--r-- 1 jpv user 0 Aug 3 11:37 oom_score
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 root -> /
-rw------- 1 jpv user 0 Aug 3 11:37 seccomp
-r--r--r-- 1 jpv user 0 Aug 3 11:37 stat
-r--r--r-- 1 jpv user 0 Aug 3 11:37 statm
-r--r--r-- 1 jpv user 0 Aug 3 11:37 status
dr-xr-xr-x 3 jpv user 0 Aug 3 11:37 task
-r--r--r-- 1 jpv user 0 Aug 3 11:37 wchan
$ chmod 7777 auxv cmdline environ fd m* o* s* task wchan
$ ls -l
total 0
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 auxv
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 cmdline
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 cwd -> ...
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 environ
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 exe -> ...
drwsrwsrwt 2 jpv user 0 Aug 3 11:37 fd
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 maps
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 mem
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 mounts
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 oom_adj
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 oom_score
lrwxrwxrwx 1 jpv user 0 Aug 3 11:37 root -> /
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 seccomp
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 stat
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 statm
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 status
drwsrwsrwt 3 jpv user 0 Aug 3 11:37 task
-rwsrwsrwt 1 jpv user 0 Aug 3 11:37 wchan
$ eatmem
malloc: Cannot allocate memory
$ ls -l
total 0
-r-------- 1 jpv user 0 Aug 3 11:44 auxv
-r--r--r-- 1 jpv user 0 Aug 3 11:44 cmdline
lrwxrwxrwx 1 jpv user 0 Aug 3 11:44 cwd -> ...
-r-------- 1 jpv user 0 Aug 3 11:44 environ
lrwxrwxrwx 1 jpv user 0 Aug 3 11:44 exe -> ...
dr-x------ 2 jpv user 0 Aug 3 11:44 fd
-r--r--r-- 1 jpv user 0 Aug 3 11:44 maps
-rw------- 1 jpv user 0 Aug 3 11:44 mem
-r--r--r-- 1 jpv user 0 Aug 3 11:44 mounts
-rw-r--r-- 1 jpv user 0 Aug 3 11:44 oom_adj
-r--r--r-- 1 jpv user 0 Aug 3 11:44 oom_score
lrwxrwxrwx 1 jpv user 0 Aug 3 11:44 root -> /
-rw------- 1 jpv user 0 Aug 3 11:44 seccomp
-r--r--r-- 1 jpv user 0 Aug 3 11:44 stat
-r--r--r-- 1 jpv user 0 Aug 3 11:44 statm
-r--r--r-- 1 jpv user 0 Aug 3 11:44 status
dr-xr-xr-x 3 jpv user 0 Aug 3 11:44 task
-r--r--r-- 1 jpv user 0 Aug 3 11:44 wchan
> Though, chmod /proc/21345 correctly yielded EPERM.
That's because the /proc/<pid> directories are S_IMMUTABLE, so the
problem doesn't arise there.
Johan Veenhuizen
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