Re: [dpdk-dev] [PATCH v3 1/2] lib/cmdline: release cl when cmdline exit

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

2021-10-13 01:53 (UTC+0000), Peng, ZhihongX:
> > -----Original Message-----
> > From: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> > Sent: Monday, October 11, 2021 4:26 PM
> > To: Peng, ZhihongX <zhihongx.peng@intel.com>
> > Cc: olivier.matz@6wind.com; dev@dpdk.org; stable@dpdk.org
> > Subject: Re: [PATCH v3 1/2] lib/cmdline: release cl when cmdline exit
> > 
> > 2021-10-08 06:41 (UTC+0000), zhihongx.peng@intel.com:  
> > > From: Zhihong Peng <zhihongx.peng@intel.com>
> > >
> > > Malloc cl in the cmdline_stdin_new function, so release in the
> > > cmdline_stdin_exit function is logical, so that cl will not be
> > > released alone.
> > >
> > > Fixes: af75078fece3 (first public release)
> > > Cc: stable@dpdk.org  
> > 
> > As I have explained before, backporting this will introduce a double-free bug
> > in user apps unless their code are fixed, so it must not be done.  
> 
> The release notes have stated that this is the only thing we can do,
> and this unreasonable design should be resolved as soon as possible.
> And the user apps change is very small.

Stable release means stable ABI, which means that a compiled binary can use
the next minor version of DPDK without recompilation. No code change is
possible in this scenario. If the behavior changes such that cmdline_exit() +
cmdline_free() worked before and now cmdline_free() cause double-free, this
is an ABI breakage. Simply put, DPDK .so are replaced, the app restarts and
crashes. Users can do nothing about that.

Release notes are for developers updating their application code for the next
DPDK version.