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([2804:1b3:a7c0:17c8:3978:9d2:1936:95b]) by smtp.gmail.com with ESMTPSA id r6-20020a05687080c600b0013bc95650c8sm2915372oab.54.2022.10.26.04.31.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Oct 2022 04:31:15 -0700 (PDT) Message-ID: <55cc0d33-b468-de1f-58f2-9016bf40566d@linaro.org> Date: Wed, 26 Oct 2022 08:31:12 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: nscd time_t size mismatch problem Content-Language: en-US To: Zev Weiss Cc: libc-alpha@sourceware.org, openbmc@lists.ozlabs.org, Wayne Tung References: <72f37987-5f8a-99c5-bd36-5153343dcf75@linaro.org> From: Adhemerval Zanella Netto Organization: Linaro In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-11.5 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,SPF_HELO_NONE,SPF_PASS,TXREP,URIBL_BLACK autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 25/10/22 22:04, Zev Weiss wrote: > On Tue, Oct 25, 2022 at 02:13:23PM PDT, Adhemerval Zanella Netto wrote: >> >> >> On 25/10/22 16:54, Zev Weiss via Libc-alpha wrote: >>> Hello glibc devs, >>> >>> We've recently been seeing some misbehavior from nscd in OpenBMC.  It >>> manifests as lots of log messages like: >>> >>>     disabled inotify-based monitoring for file /passwd': No such file or directory >>>     stat failed for file /passwd'; will try again later: No such file or directory >>>     disabled inotify-based monitoring for file /group': No such file or directory >>>     stat failed for file /group'; will try again later: No such file or directory >>>     disabled inotify-based monitoring for file /hosts': No such file or directory >>>     stat failed for file /hosts'; will try again later: No such file or directory >>>     disabled inotify-based monitoring for file /resolv.conf': No such file or directory >>>     stat failed for file /resolv.conf'; will try again later: No such file or directory >>> >>> and so forth.  I initially assumed it was a configure-time --sysconfdir mixup, but after digging into it I found that it actually stems from a time_t size mismatch (this is a 32-bit ARM gnueabi target): >>> >>>     $ gdb -batch -ex 'pt time_t' -ex 'p sizeof(time_t)' time/time.o >>>     type = long >>>     $1 = 4 >>>     $ gdb -batch -ex 'pt time_t' -ex 'p sizeof(time_t)' nscd/nscd.o >>>     type = long long >>>     $1 = 8 >>> >>> The confusing log messages are thus just the result of the coincidence that sizeof(long long) - sizeof(long) == strlen("/etc"), which causes the disagreement in the layout of struct traced_file to make it look like the 'fname' member just had its directory prefix chopped off. >>> >>> In the discussion of the bug in the OpenBMC issue tracker [0], Wayne Tung (CCed) came up with the patch below, which does seem to solve the immediate problem, but if I'm understanding things right does so by just reverting nscd to a 32-bit time_t, and so I'd expect probably wouldn't be considered the "right" fix -- however I don't presently know enough about the 32/64-bit time_t transition and ensuing compatibility concerns to know what the right fix really is.  Should nscd perhaps be using __time64_t or something instead of time_t? >> >> Reverting to 32 bits time_t only means that we are postponing some potential >> failure to y2038, we really move everything to 64 bit time_t.  Could you check >> if the following patch fix it? >> >> The issue is we do build nss modules with 64 time_t, however some features >> are built on libc.so itself and in such cases we need to explicit use the >> internal __time64_t type. >> >> diff --git a/nscd/nscd.h b/nscd/nscd.h >> index 368091aef8..f15321585b 100644 >> --- a/nscd/nscd.h >> +++ b/nscd/nscd.h >> @@ -65,7 +65,7 @@ typedef enum >> struct traced_file >> { >>   /* Tracks the last modified time of the traced file.  */ >> -  time_t mtime; >> +  __time64_t mtime; >>   /* Support multiple registered files per database.  */ >>   struct traced_file *next; >>   int call_res_init; >> > > Ah, great -- after testing that out I can confirm that it appears to fix the problem.  Thanks! > > Also, after sending that email I discovered that there's an existing bugzilla issue for this same problem (https://sourceware.org/bugzilla/show_bug.cgi?id=29402), so that can presumably be closed once a fix is committed. I will send a proper path and I will check if there are any other instance of time_t that is used internally as this.