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SubjectRe: [PATCH v1 1/1] Firstly, as Andy mentioned, this should be smp_rmb() instead of rmb(). considering that TSYNC is a cross-thread situation, and rmb() is a mandatory barrier which should not be used to control SMP effects, since mandatory barriers impos
Hi wanghongzhe,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on v5.11-rc6]
[also build test WARNING on next-20210125]
[cannot apply to kees/for-next/seccomp]
[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]

url: https://github.com/0day-ci/linux/commits/wanghongzhe/Firstly-as-Andy-mentioned-this-should-be-smp_rmb-instead-of-rmb-considering-that-TSYNC-is-a-cross-thread-situation-and-r/20210202-173311
base: 1048ba83fb1c00cd24172e23e8263972f6b5d9ac
config: i386-randconfig-s001-20210202 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.3-215-g0fb77bb6-dirty
# https://github.com/0day-ci/linux/commit/f79414957fc8acb6b680bbcd26fa987328a5724a
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review wanghongzhe/Firstly-as-Andy-mentioned-this-should-be-smp_rmb-instead-of-rmb-considering-that-TSYNC-is-a-cross-thread-situation-and-r/20210202-173311
git checkout f79414957fc8acb6b680bbcd26fa987328a5724a
# save the attached .config to linux build tree
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=i386

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

kernel/seccomp.c: In function '__secure_computing':
>> kernel/seccomp.c:1313:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
1313 | if (unlikely(current->seccomp.mode != SECCOMP_MODE_FILTER))
| ^
kernel/seccomp.c:1315:2: note: here
1315 | case SECCOMP_MODE_FILTER:
| ^~~~


vim +1313 kernel/seccomp.c

1283
1284 int __secure_computing(const struct seccomp_data *sd)
1285 {
1286 int this_syscall;
1287
1288 if (IS_ENABLED(CONFIG_CHECKPOINT_RESTORE) &&
1289 unlikely(current->ptrace & PT_SUSPEND_SECCOMP))
1290 return 0;
1291
1292 this_syscall = sd ? sd->nr :
1293 syscall_get_nr(current, current_pt_regs());
1294
1295 /*
1296 * Make sure that any changes to mode from another thread have
1297 * been seen after SYSCALL_WORK_SECCOMP was seen.
1298 */
1299 smp_rmb();
1300
1301 switch (current->seccomp.mode) {
1302 case SECCOMP_MODE_STRICT:
1303 __secure_computing_strict(this_syscall); /* may call do_exit */
1304 return 0;
1305 /*
1306 * Make sure that change to mode (from SECCOMP_MODE_DISABLED to
1307 * SECCOMP_MODE_FILTER) from another thread using TSYNC ability
1308 * have been seen after SYSCALL_WORK_SECCOMP was seen. Read mode again behind
1309 * smp_rmb(), if it equals SECCOMP_MODE_FILTER, go to the right path.
1310 */
1311 case SECCOMP_MODE_DISABLED:
1312 smp_rmb();
> 1313 if (unlikely(current->seccomp.mode != SECCOMP_MODE_FILTER))
1314 BUG();
1315 case SECCOMP_MODE_FILTER:
1316 return __seccomp_filter(this_syscall, sd, false);
1317 default:
1318 BUG();
1319 }
1320 }
1321 #endif /* CONFIG_HAVE_ARCH_SECCOMP_FILTER */
1322

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
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