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Date: Tue, 31 Aug 2021 15:48:36 +0800
From: kernel test robot <yujie.liu@...el.com>
To: Eric Dumazet <eric.dumazet@...il.com>,
"David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
CC: <llvm@...ts.linux.dev>, <kbuild-all@...ts.01.org>,
netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>, Willy Tarreau <w@....eu>,
Keyu Man <kman001@....edu>, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH net 2/2] ipv4: make exception cache less predictible
Hi Eric,
I love your patch! Perhaps something to improve:
[auto build test WARNING on net/master]
url: https://github.com/0day-ci/linux/commits/Eric-Dumazet/inet-make-exception-handling-less-predictible/20210830-061726
base: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 57f780f1c43362b86fd23d20bd940e2468237716
:::::: branch date: 19 hours ago
:::::: commit date: 19 hours ago
config: x86_64-randconfig-c007-20210830 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project 4b1fde8a2b681dad2ce0c082a5d6422caa06b0bc)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/adf305d00ec06cb771dc960f0d7bd62d07561371
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Eric-Dumazet/inet-make-exception-handling-less-predictible/20210830-061726
git checkout adf305d00ec06cb771dc960f0d7bd62d07561371
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 clang-analyzer
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>
clang-analyzer warnings: (new ones prefixed by >>)
>> net/ipv4/route.c:575:7: warning: Dereference of null pointer [clang-analyzer-core.NullDereference]
rt = rcu_dereference(fnhe->fnhe_rth_input);
^
net/ipv4/route.c:592:34: note: 'oldest' initialized to a null pointer value
struct fib_nh_exception *fnhe, *oldest = NULL;
^~~~~~
net/ipv4/route.c:594:2: note: Loop condition is true. Entering loop body
for (fnhe_p = &hash->chain; ; fnhe_p = &fnhe->fnhe_next) {
^
net/ipv4/route.c:595:10: note: Assuming the condition is false
fnhe = rcu_dereference_protected(*fnhe_p,
^
include/linux/rcupdate.h:587:2: note: expanded from macro 'rcu_dereference_protected'
__rcu_dereference_protected((p), (c), __rcu)
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/rcupdate.h:396:19: note: expanded from macro '__rcu_dereference_protected'
RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \
~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/rcupdate.h:318:8: note: expanded from macro 'RCU_LOCKDEP_WARN'
if ((c) && debug_lockdep_rcu_enabled() && !__warned) { \
^
net/ipv4/route.c:595:10: note: Left side of '&&' is false
fnhe = rcu_dereference_protected(*fnhe_p,
^
include/linux/rcupdate.h:587:2: note: expanded from macro 'rcu_dereference_protected'
__rcu_dereference_protected((p), (c), __rcu)
^
include/linux/rcupdate.h:396:2: note: expanded from macro '__rcu_dereference_protected'
RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \
^
include/linux/rcupdate.h:318:11: note: expanded from macro 'RCU_LOCKDEP_WARN'
if ((c) && debug_lockdep_rcu_enabled() && !__warned) { \
^
net/ipv4/route.c:595:10: note: Loop condition is false. Exiting loop
fnhe = rcu_dereference_protected(*fnhe_p,
^
include/linux/rcupdate.h:587:2: note: expanded from macro 'rcu_dereference_protected'
__rcu_dereference_protected((p), (c), __rcu)
^
include/linux/rcupdate.h:396:2: note: expanded from macro '__rcu_dereference_protected'
RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \
^
include/linux/rcupdate.h:316:2: note: expanded from macro 'RCU_LOCKDEP_WARN'
do { \
^
net/ipv4/route.c:597:7: note: Assuming 'fnhe' is null
if (!fnhe)
^~~~~
net/ipv4/route.c:597:3: note: Taking true branch
if (!fnhe)
^
net/ipv4/route.c:598:4: note: Execution continues on line 605
break;
^
net/ipv4/route.c:605:20: note: Passing null pointer value via 1st parameter 'fnhe'
fnhe_flush_routes(oldest);
^~~~~~
net/ipv4/route.c:605:2: note: Calling 'fnhe_flush_routes'
fnhe_flush_routes(oldest);
^~~~~~~~~~~~~~~~~~~~~~~~~
net/ipv4/route.c:575:7: warning: Dereference of null pointer [clang-analyzer-core.NullDereference]
rt = rcu_dereference(fnhe->fnhe_rth_input);
^
vim +575 net/ipv4/route.c
4895c771c7f006 David S. Miller 2012-07-17 570
2ffae99d1fac27 Timo Teräs 2013-06-27 571 static void fnhe_flush_routes(struct fib_nh_exception *fnhe)
2ffae99d1fac27 Timo Teräs 2013-06-27 572 {
2ffae99d1fac27 Timo Teräs 2013-06-27 573 struct rtable *rt;
2ffae99d1fac27 Timo Teräs 2013-06-27 574
2ffae99d1fac27 Timo Teräs 2013-06-27 @575 rt = rcu_dereference(fnhe->fnhe_rth_input);
2ffae99d1fac27 Timo Teräs 2013-06-27 576 if (rt) {
2ffae99d1fac27 Timo Teräs 2013-06-27 577 RCU_INIT_POINTER(fnhe->fnhe_rth_input, NULL);
95c47f9cf5e028 Wei Wang 2017-06-17 578 dst_dev_put(&rt->dst);
0830106c539001 Wei Wang 2017-06-17 579 dst_release(&rt->dst);
2ffae99d1fac27 Timo Teräs 2013-06-27 580 }
2ffae99d1fac27 Timo Teräs 2013-06-27 581 rt = rcu_dereference(fnhe->fnhe_rth_output);
2ffae99d1fac27 Timo Teräs 2013-06-27 582 if (rt) {
2ffae99d1fac27 Timo Teräs 2013-06-27 583 RCU_INIT_POINTER(fnhe->fnhe_rth_output, NULL);
95c47f9cf5e028 Wei Wang 2017-06-17 584 dst_dev_put(&rt->dst);
0830106c539001 Wei Wang 2017-06-17 585 dst_release(&rt->dst);
2ffae99d1fac27 Timo Teräs 2013-06-27 586 }
2ffae99d1fac27 Timo Teräs 2013-06-27 587 }
2ffae99d1fac27 Timo Teräs 2013-06-27 588
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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