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[PATCH] net: sched: drr: dont intepret cls results when asked to drop

Ma Ke posted 1 patch 2 years, 4 months ago 
net/sched/sch_drr.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
[PATCH] net: sched: drr: dont intepret cls results when asked to drop
Posted by Ma Ke 2 years, 4 months ago 
If asked to drop a packet via TC_ACT_SHOT it is unsafe to
assume that res.class contains a valid pointer.

Signed-off-by: Ma Ke <make_ruc2021@163.com>
---
 net/sched/sch_drr.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index 19901e77cd3b..a535dc3b0e05 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -310,6 +310,8 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
 	fl = rcu_dereference_bh(q->filter_list);
 	result = tcf_classify(skb, NULL, fl, &res, false);
 	if (result >= 0) {
+		if (result == TC_ACT_SHOT)
+			return NULL;
 #ifdef CONFIG_NET_CLS_ACT
 		switch (result) {
 		case TC_ACT_QUEUED:
@@ -317,8 +319,6 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
 		case TC_ACT_TRAP:
 			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
 			fallthrough;
-		case TC_ACT_SHOT:
-			return NULL;
 		}
 #endif
 		cl = (struct drr_class *)res.class;
-- 
2.37.2
Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop
Posted by kernel test robot 2 years, 4 months ago 
Hi Ma,

kernel test robot noticed the following build errors:

[auto build test ERROR on net-next/main]
[also build test ERROR on net/main linus/master v6.6-rc1 next-20230915]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Ma-Ke/net-sched-drr-dont-intepret-cls-results-when-asked-to-drop/20230915-223913
base:   net-next/main
patch link:    https://lore.kernel.org/r/20230915142056.3411330-1-make_ruc2021%40163.com
patch subject: [PATCH] net: sched: drr: dont intepret cls results when asked to drop
config: x86_64-rhel-8.3-rust (https://download.01.org/0day-ci/archive/20230916/202309161334.0j3RBkmV-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20230916/202309161334.0j3RBkmV-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202309161334.0j3RBkmV-lkp@intel.com/

All errors (new ones prefixed by >>):

>> net/sched/sch_drr.c:321:4: error: fallthrough annotation does not directly precede switch label
                           fallthrough;
                           ^
   include/linux/compiler_attributes.h:227:41: note: expanded from macro 'fallthrough'
   # define fallthrough                    __attribute__((__fallthrough__))
                                           ^
   1 error generated.


vim +321 net/sched/sch_drr.c

13d2a1d2b032de Patrick McHardy     2008-11-20  293  
13d2a1d2b032de Patrick McHardy     2008-11-20  294  static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
13d2a1d2b032de Patrick McHardy     2008-11-20  295  				      int *qerr)
13d2a1d2b032de Patrick McHardy     2008-11-20  296  {
13d2a1d2b032de Patrick McHardy     2008-11-20  297  	struct drr_sched *q = qdisc_priv(sch);
13d2a1d2b032de Patrick McHardy     2008-11-20  298  	struct drr_class *cl;
13d2a1d2b032de Patrick McHardy     2008-11-20  299  	struct tcf_result res;
25d8c0d55f241c John Fastabend      2014-09-12  300  	struct tcf_proto *fl;
13d2a1d2b032de Patrick McHardy     2008-11-20  301  	int result;
13d2a1d2b032de Patrick McHardy     2008-11-20  302  
13d2a1d2b032de Patrick McHardy     2008-11-20  303  	if (TC_H_MAJ(skb->priority ^ sch->handle) == 0) {
13d2a1d2b032de Patrick McHardy     2008-11-20  304  		cl = drr_find_class(sch, skb->priority);
13d2a1d2b032de Patrick McHardy     2008-11-20  305  		if (cl != NULL)
13d2a1d2b032de Patrick McHardy     2008-11-20  306  			return cl;
13d2a1d2b032de Patrick McHardy     2008-11-20  307  	}
13d2a1d2b032de Patrick McHardy     2008-11-20  308  
13d2a1d2b032de Patrick McHardy     2008-11-20  309  	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
25d8c0d55f241c John Fastabend      2014-09-12  310  	fl = rcu_dereference_bh(q->filter_list);
3aa2605594556c Davide Caratti      2021-07-28  311  	result = tcf_classify(skb, NULL, fl, &res, false);
13d2a1d2b032de Patrick McHardy     2008-11-20  312  	if (result >= 0) {
13abeaf39ca823 Ma Ke               2023-09-15  313  		if (result == TC_ACT_SHOT)
13abeaf39ca823 Ma Ke               2023-09-15  314  			return NULL;
13d2a1d2b032de Patrick McHardy     2008-11-20  315  #ifdef CONFIG_NET_CLS_ACT
13d2a1d2b032de Patrick McHardy     2008-11-20  316  		switch (result) {
13d2a1d2b032de Patrick McHardy     2008-11-20  317  		case TC_ACT_QUEUED:
13d2a1d2b032de Patrick McHardy     2008-11-20  318  		case TC_ACT_STOLEN:
e25ea21ffa66a0 Jiri Pirko          2017-06-06  319  		case TC_ACT_TRAP:
13d2a1d2b032de Patrick McHardy     2008-11-20  320  			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
964201de695b8a Gustavo A. R. Silva 2020-07-07 @321  			fallthrough;
13d2a1d2b032de Patrick McHardy     2008-11-20  322  		}
13d2a1d2b032de Patrick McHardy     2008-11-20  323  #endif
13d2a1d2b032de Patrick McHardy     2008-11-20  324  		cl = (struct drr_class *)res.class;
13d2a1d2b032de Patrick McHardy     2008-11-20  325  		if (cl == NULL)
13d2a1d2b032de Patrick McHardy     2008-11-20  326  			cl = drr_find_class(sch, res.classid);
13d2a1d2b032de Patrick McHardy     2008-11-20  327  		return cl;
13d2a1d2b032de Patrick McHardy     2008-11-20  328  	}
13d2a1d2b032de Patrick McHardy     2008-11-20  329  	return NULL;
13d2a1d2b032de Patrick McHardy     2008-11-20  330  }
13d2a1d2b032de Patrick McHardy     2008-11-20  331  

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Re: [PATCH] net: sched: drr: dont intepret cls results when asked to drop
Posted by Vadim Fedorenko 2 years, 4 months ago 
On 15/09/2023 15:20, Ma Ke wrote:
> If asked to drop a packet via TC_ACT_SHOT it is unsafe to
> assume that res.class contains a valid pointer.
> 
> Signed-off-by: Ma Ke <make_ruc2021@163.com>
> ---
>   net/sched/sch_drr.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
> index 19901e77cd3b..a535dc3b0e05 100644
> --- a/net/sched/sch_drr.c
> +++ b/net/sched/sch_drr.c
> @@ -310,6 +310,8 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
>   	fl = rcu_dereference_bh(q->filter_list);
>   	result = tcf_classify(skb, NULL, fl, &res, false);
>   	if (result >= 0) {
> +		if (result == TC_ACT_SHOT)
> +			return NULL;

With CONFIG_NET_CLS_ACT undefined tcf_classify can only return
TC_ACT_UNSPEC and the if statement above is always false.

Do you have any real issue you are trying to fix?

>   #ifdef CONFIG_NET_CLS_ACT
>   		switch (result) {
>   		case TC_ACT_QUEUED:
> @@ -317,8 +319,6 @@ static struct drr_class *drr_classify(struct sk_buff *skb, struct Qdisc *sch,
>   		case TC_ACT_TRAP:
>   			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
>   			fallthrough;
> -		case TC_ACT_SHOT:
> -			return NULL;
>   		}
>   #endif
>   		cl = (struct drr_class *)res.class;

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