Re: [PATCH 11/15] prlimit: avoid segfault due to array-out-of-bounds error

[Karel Zak <kzak@redhat.com>]

On Mon, Nov 14, 2011 at 02:48:41AM +0100, Bernhard Voelker wrote:
> [PATCH 11/15] prlimit: avoid segfault due to array-out-of-bounds error
>
> prlimit used 1 element of the lims array per limit given on the command
> line argument, not being aware that a user would pass the value of the
> soft and the hard limit in different options - leading to a segfault
> when the user passes more than MAX_RESOURCES limit options.
> As a side effect, a limit was retrieved and printed several times if
> the corresponding option appeared multiple times.
>
> Example:
> $ prlimit -l -l -l -l -l -l -l -l -l -l -l -l -l -l -l -l -l -l -l
> RESOURCE DESCRIPTION                         SOFT   HARD UNITS
> MEMLOCK  max locked-in-memory address space 65536 262144 bytes
> MEMLOCK  max locked-in-memory address space 65536 262144 bytes
> ...
> Segmentation fault

 Ah.. stupid bug.

> Use the lims array in a more direct way, i.e. the index is limit id.
> Initialize lims array and adapt option parsing in main() accordingly.
> do_prlimits() and show_limits(): loop over all MAX_RESOURCES in the
> lims array.

 It means that users cannot control order of the printed and modified
 resources. We prefer in all our new utils that output is fully
 controlled by users -- only this is a way how you can create stable
 and robust scripts.

 I have replaced the array with list (see include/list.h). This
 solution makes the code more readable and robust.

 # ./prlimit --data --nofile
 RESOURCE DESCRIPTION                   SOFT      HARD UNITS
 DATA     max data size            unlimited unlimited bytes
 NOFILE   max amount of open files      1001      3000 

 # ./prlimit --nofile --data
 RESOURCE DESCRIPTION                   SOFT      HARD UNITS
 NOFILE   max amount of open files      1001      3000 
 DATA     max data size            unlimited unlimited bytes

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com