Re: [stable:linux-5.4.y 3300/8640] net/sched/cls_flower.c:296:12: warning: stack frame size (1040) exceeds limit (1024) in 'fl_classify'

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Jun 05, 2023 at 08:32:09AM -0700, Nathan Chancellor wrote:
> On Mon, Jun 05, 2023 at 03:11:24PM +0300, Vlad Buslov wrote:
> > On Mon 05 Jun 2023 at 18:59, kernel test robot <lkp@intel.com> wrote:
> > > Hi Vlad,
> > >
> > > First bad commit (maybe != root cause):
> > >
> > > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git linux-5.4.y
> > > head:   cf0b1e5482eaeb4db15c9e703267483dba88b575
> > > commit: 5f2e54391893c67b709a64b280417ca0318adb73 [3300/8640] net/sched: flower: fix parsing of ethertype following VLAN header
> > > config: mips-randconfig-r013-20230605 (https://download.01.org/0day-ci/archive/20230605/202306051816.mO3hqt7d-lkp@intel.com/config)
> > > compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project 4faf3aaf28226a4e950c103a14f6fc1d1fdabb1b)
> > > reproduce (this is a W=1 build):
> > >         mkdir -p ~/bin
> > >         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
> > >         chmod +x ~/bin/make.cross
> > >         # install mips cross compiling tool for clang build
> > >         # apt-get install binutils-mipsel-linux-gnu
> > >         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=5f2e54391893c67b709a64b280417ca0318adb73
> > >         git remote add stable https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
> > >         git fetch --no-tags stable linux-5.4.y
> > >         git checkout 5f2e54391893c67b709a64b280417ca0318adb73
> > >         # save the config file
> > >         mkdir build_dir && cp config build_dir/.config
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=mips olddefconfig
> > >         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash net/sched/
> > >
> > > If you fix the issue, kindly add following tag where applicable
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Closes: https://lore.kernel.org/oe-kbuild-all/202306051816.mO3hqt7d-lkp@intel.com/
> > >
> > > All warnings (new ones prefixed by >>):
> > >
> > >>> net/sched/cls_flower.c:296:12: warning: stack frame size (1040) exceeds limit (1024) in 'fl_classify' [-Wframe-larger-than]
> > >    static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
> > >               ^
> > >    1 warning generated.
> > >
> > >
> > > vim +/fl_classify +296 net/sched/cls_flower.c
> > >
> > > e0ace68af2acfe Paul Blakey            2019-07-09  295  
> > > 77b9900ef53ae0 Jiri Pirko             2015-05-12 @296  static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp,
> > > 77b9900ef53ae0 Jiri Pirko             2015-05-12  297  		       struct tcf_result *res)
> > > 77b9900ef53ae0 Jiri Pirko             2015-05-12  298  {
> > > 77b9900ef53ae0 Jiri Pirko             2015-05-12  299  	struct cls_fl_head *head = rcu_dereference_bh(tp->root);
> > > 77b9900ef53ae0 Jiri Pirko             2015-05-12  300  	struct fl_flow_key skb_mkey;
> > 
> > The stack usage of fl_classify() has already been addressed in later
> > kernels by commit 0af413bd3e2d ("flow_dissector: work around stack frame
> > size warning") which moved mkey into fl_mask_lookup(). Not sure what
> > else can be done since my commit just adds a new flow dissector fields
> > that are needed to correctly parse packets with multiple VLAN headers.
> 
> 0af413bd3e2d seems like a reasonable cherry-pick for linux-5.4.y to me
> if the warning is showing up there, which seems like the only thing that
> needs to be done for this report.

That sounds good to me, now picked!

greg k-h