linux-kernel - Re: [PATCH 4/4] audit: check if queue is full after prepare_to_wait

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Date:   Tue, 9 May 2023 01:44:14 +0000
From:   Eiichi Tsukata <eiichi.tsukata@...anix.com>
To:     kernel test robot <lkp@...el.com>
CC:     Paul Moore <paul@...l-moore.com>,
        "eparis@...hat.com" <eparis@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "audit@...r.kernel.org" <audit@...r.kernel.org>,
        "llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
        "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>
Subject: Re: [PATCH 4/4] audit: check if queue is full after
 prepare_to_wait_exclusive()



> On May 9, 2023, at 2:13, kernel test robot <lkp@...el.com> wrote:
> 
> Hi Eiichi,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on pcmoore-audit/next]
> [also build test WARNING on linus/master v6.4-rc1 next-20230508]
> [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://urldefense.proofpoint.com/v2/url?u=https-3A__git-2Dscm.com_docs_git-2Dformat-2Dpatch-23-5Fbase-5Ftree-5Finformation&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=hJmkWbARWhiKbVA6rbRJyTnRSNu6CCcbc8h_5kv9OMs&e= ]
> 
> url:    https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_intel-2Dlab-2Dlkp_linux_commits_Eiichi-2DTsukata_audit-2Drefactor-2Dqueue-2Dfull-2Dchecks_20230508-2D160019&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=SgsiWqTcS-KNlz7pbWtpJLkfU4NCNx1PPnf561OBl_Y&e= 
> base:   https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pub_scm_linux_kernel_git_pcmoore_audit.git&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=ODnLSauQV_XYtGzJFN1XMH7WQhUdZfa4kgzeiRdieOk&e=  next
> patch link:    https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_r_20230508075812.76077-2D5-2Deiichi.tsukata-2540nutanix.com&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=xz0pVOvfxWhxF6yp8r3GFk7YmDc34ntJLAvFhHkVWqo&e= 
> patch subject: [PATCH 4/4] audit: check if queue is full after prepare_to_wait_exclusive()
> config: i386-randconfig-a001-20230508 (https://urldefense.proofpoint.com/v2/url?u=https-3A__download.01.org_0day-2Dci_archive_20230509_202305090112.uJSc0NBw-2Dlkp-40intel.com_config&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=q5366dSfHPWCbkUzXNPdIjJ8BOj2forT0D4fl3XwOQM&e= )
> compiler: clang version 14.0.6 (https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_llvm_llvm-2Dproject&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=cVl2Fv0ruc2lDCYKGZ2MsG1xkcmDSm0yVdz_UYbBk2A&e=  f28c006a5895fc0e329fe15fead81e37457cb1d1)
> reproduce (this is a W=1 build):
>        wget https://urldefense.proofpoint.com/v2/url?u=https-3A__raw.githubusercontent.com_intel_lkp-2Dtests_master_sbin_make.cross&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=Uwk-WxemwAN0EiTlBE5VBdk5GGUUOMySKGZXEEpkDBM&e=  -O ~/bin/make.cross
>        chmod +x ~/bin/make.cross
>        # https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_intel-2Dlab-2Dlkp_linux_commit_cbc69d0c34bdbc06ebca3e3020cfc24034fcf173&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=RWanBTSRB28iteIUKeSVppj2xq4uJygfumsMWjJv5jI&e= 
>        git remote add linux-review https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_intel-2Dlab-2Dlkp_linux&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=14mmQ3GZhIozHeufPooQIuKd1O2SeFL8-1gIi9c79EM&e= 
>        git fetch --no-tags linux-review Eiichi-Tsukata/audit-refactor-queue-full-checks/20230508-160019
>        git checkout cbc69d0c34bdbc06ebca3e3020cfc24034fcf173
>        # save the config file
>        mkdir build_dir && cp config build_dir/.config
>        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 olddefconfig
>        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@...el.com>
> | Link: https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_oe-2Dkbuild-2Dall_202305090112.uJSc0NBw-2Dlkp-40intel.com_&d=DwIBAg&c=s883GpUCOChKOHiocYtGcg&r=dy01Dr4Ly8mhvnUdx1pZhhT1bkq4h9z5aVWu3paoZtk&m=iEsfAln6T0-ALFZ77M_oT-wS2T2UFxboG589BXhqJFYG7-pvNIFPZ_GOAcQLlAj7&s=cKrS8zKrWpbCBg5KOGiZDk0iqjUu9BXkChKAu4pMC2Q&e= 
> 
> All warnings (new ones prefixed by >>):
> 
>>> kernel/audit.c:651:6: warning: variable 'rtime' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
>           if (audit_queue_full(&audit_queue)) {
>               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   kernel/audit.c:657:9: note: uninitialized use occurs here
>           return rtime;
>                  ^~~~~
>   kernel/audit.c:651:2: note: remove the 'if' if its condition is always true
>           if (audit_queue_full(&audit_queue)) {
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   kernel/audit.c:642:12: note: initialize the variable 'rtime' to silence this warning
>           long rtime;
>                     ^
>                      = 0
>   1 warning generated.
> 

Nice catch thanks!
We can initialize rtime as you suggested but in this case it will be better to return 0
explicitly if there is some room in the queue. i.e:

diff --git a/kernel/audit.c b/kernel/audit.c
index d37a3a045230..6b0cc0459984 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -651,6 +651,8 @@ static long wait_for_kauditd(long stime)
        if (audit_queue_full(&audit_queue)) {
                rtime = schedule_timeout(stime);
                atomic_add(stime - rtime, &audit_backlog_wait_time_actual);
+       } else {
+               rtime = 0;
        }
        finish_wait(&audit_backlog_wait, &wait);

I’ll fix it in v2.

Eiichi