# [PATCH] Do not trust PWD blindly 8 messages from 2011-07-09 to 2011-07-11. Participants: Johannes Schindelin, Sebastian Schuberth, Johannes Sixt, Randal L. Schwartz, Junio C Hamano. Thread: https://gitlist.dev/t/27781 ## Johannes Schindelin, 2011-07-09 17:38 Subject: [PATCH] Do not trust PWD blindly Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.1107091935210.1985%40bonsai2 In-Reply-To: ``` At least on Windows, chdir() does not update PWD. Unfortunately, stat() does not fill any ino or dev fields anymore, so get_pwd_cwd() is not able to tell. But there is a telltale: both ino and dev are 0 when they are not filled correctly, so let's be extra cautious. This happens to fix a bug in "get-receive-pack working_directory/" when the GIT_DIR would not be set correctly due to absolute_path(".") returning the wrong value. Signed-off-by: Johannes Schindelin --- On Fri, 8 Jul 2011, Pat Thoyts wrote: > ! t5516-fetch-push (60 receive.denyCurrentBranch = updateInstead) This patch fixes that. Hannes, I have no idea whether you meant 10c4c881 to fix anything on Windows. abspath.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/abspath.c b/abspath.c index 01858eb..37287f8 100644 --- a/abspath.c +++ b/abspath.c @@ -102,7 +102,8 @@ static const char *get_pwd_cwd(void) pwd = getenv("PWD"); if (pwd && strcmp(pwd, cwd)) { stat(cwd, &cwd_stat); - if (!stat(pwd, &pwd_stat) && + if ((cwd_stat.st_dev || cwd_stat.st_ino) && + !stat(pwd, &pwd_stat) && pwd_stat.st_dev == cwd_stat.st_dev && pwd_stat.st_ino == cwd_stat.st_ino) { strlcpy(cwd, pwd, PATH_MAX); -- 1.7.6.rc0.4047.g15f89 ``` ## Sebastian Schuberth, 2011-07-09 20:06 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: URL: https://gitlist.dev/e/CAHGBnuO_p8WfBowiBw%3D4t8432nc0UvpNS_emWZEYBn1zNY%2Bc5Q%40mail.gmail.com In-Reply-To: ``` On Sat, Jul 9, 2011 at 19:38, Johannes Schindelin wrote: >        On Fri, 8 Jul 2011, Pat Thoyts wrote: > >        > ! t5516-fetch-push      (60 receive.denyCurrentBranch = updateInstead) > >        This patch fixes that. I can confirm that the patch fixes test 5516 on Windows. Thanks Dscho! -- Sebastian Schuberth ``` ## Johannes Sixt, 2011-07-10 20:47 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: <4E1A0FCC.7080308@kdbg.org> URL: https://gitlist.dev/e/4E1A0FCC.7080308%40kdbg.org In-Reply-To: ``` Am 09.07.2011 19:38, schrieb Johannes Schindelin: > > At least on Windows, chdir() does not update PWD. Very strange wording. chdir() should not update PWD even on POSIX. > Unfortunately, stat() > does not fill any ino or dev fields anymore, so get_pwd_cwd() is not > able to tell. > > But there is a telltale: both ino and dev are 0 when they are not filled > correctly, so let's be extra cautious. > > This happens to fix a bug in "get-receive-pack working_directory/" when > the GIT_DIR would not be set correctly due to absolute_path(".") > returning the wrong value. > > Signed-off-by: Johannes Schindelin > --- > > On Fri, 8 Jul 2011, Pat Thoyts wrote: > > > ! t5516-fetch-push (60 receive.denyCurrentBranch = updateInstead) > > This patch fixes that. > > Hannes, I have no idea whether you meant 10c4c881 to fix anything > on Windows. I think this fix worked for me because when git is called from CMD, PWD is not in the enviornment and the if (pwd && ...) branch is never taken. > > abspath.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/abspath.c b/abspath.c > index 01858eb..37287f8 100644 > --- a/abspath.c > +++ b/abspath.c > @@ -102,7 +102,8 @@ static const char *get_pwd_cwd(void) > pwd = getenv("PWD"); > if (pwd && strcmp(pwd, cwd)) { > stat(cwd, &cwd_stat); > - if (!stat(pwd, &pwd_stat) && > + if ((cwd_stat.st_dev || cwd_stat.st_ino) && > + !stat(pwd, &pwd_stat) && > pwd_stat.st_dev == cwd_stat.st_dev && > pwd_stat.st_ino == cwd_stat.st_ino) { > strlcpy(cwd, pwd, PATH_MAX); Acked-by: Johannes Sixt -- Hannes ``` ## Johannes Schindelin, 2011-07-10 22:59 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.1107110057120.3379%40bonsai2 In-Reply-To: <4E1A0FCC.7080308@kdbg.org> ``` Hi, On Sun, 10 Jul 2011, Johannes Sixt wrote: > Am 09.07.2011 19:38, schrieb Johannes Schindelin: > > > > At least on Windows, chdir() does not update PWD. > > Very strange wording. chdir() should not update PWD even on POSIX. Well, you might think it is strange wording. But then, it expresses exactly what I meant it to say. chdir() does not update PWD on Windows. You might be very surprised, but that is not true on the Linux system where one of the 4msysgit.git test cases does _not_ break, while it does on Windows. I hoped to make that clear with the wording, but apparently I failed rather blatantly. All the more surprising do I find that: > Acked-by: Johannes Sixt Ciao, Johannes ``` ## Randal L. Schwartz, 2011-07-11 01:52 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: <86k4bpporf.fsf@red.stonehenge.com> URL: https://gitlist.dev/e/86k4bpporf.fsf%40red.stonehenge.com In-Reply-To: ``` >>>>> "Johannes" == Johannes Schindelin writes: Johannes> You might be very surprised, but that is not true on the Linux system Johannes> where one of the 4msysgit.git test cases does _not_ break, while it does Johannes> on Windows. If you ever depend on a userspace PWD to be your actual current directory without at least stat()ing it, you've failed. In my experience, it is *never* reliable. It's just a hint. -- Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095 Smalltalk/Perl/Unix consulting, Technical writing, Comedy, etc. etc. See http://methodsandmessages.posterous.com/ for Smalltalk discussion ``` ## Johannes Schindelin, 2011-07-11 09:26 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.1107111121390.3379%40bonsai2 In-Reply-To: <86k4bpporf.fsf@red.stonehenge.com> ``` Hi Randal, On Sun, 10 Jul 2011, Randal L. Schwartz wrote: > >>>>> "Johannes" == Johannes Schindelin writes: > > Johannes> You might be very surprised, but that is not true on the Linux > Johannes> system where one of the 4msysgit.git test cases does _not_ > Johannes> break, while it does on Windows. > > If you ever depend on a userspace PWD to be your actual current > directory without at least stat()ing it, you've failed. > > In my experience, it is *never* reliable. It's just a hint. To be precise, get_pwd_cwd() _does_ stat() what's in PWD, and _does_ compare with the stat() of what comes out of getcwd(), but that comparison uses only st_dev and st_ino, both of which happen to be 0 in my case -- for each and every file/directory. I can only _guess_ at the reasoning behind get_pwd_cwd(). I _think_ it was meant to catch the case when getcwd() and PWD refer to the same directory, but PWD goes through symbolic links. I was tempted to just throw that PWD handling out for Windows, since we do not have symbolic link handling yet. But that is currently actively discussed, so we might need it in the future, in which case I have to figure out how to fake reliable st_dev and st_ino values into our stat() code. Ciao, Dscho ``` ## Junio C Hamano, 2011-07-11 16:56 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: <7vbox0g3hn.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vbox0g3hn.fsf%40alter.siamese.dyndns.org In-Reply-To: ``` Johannes Schindelin writes: > On Sun, 10 Jul 2011, Randal L. Schwartz wrote: > ... >> If you ever depend on a userspace PWD to be your actual current >> directory without at least stat()ing it, you've failed. >> >> In my experience, it is *never* reliable. It's just a hint. > > To be precise, get_pwd_cwd() _does_ stat() what's in PWD, and _does_ > compare with the stat() of what comes out of getcwd(), but that comparison > uses only st_dev and st_ino, both of which happen to be 0 in my case -- > for each and every file/directory. > > I can only _guess_ at the reasoning behind get_pwd_cwd(). I _think_ it was > meant to catch the case when getcwd() and PWD refer to the same directory, > but PWD goes through symbolic links. Thanks for a much clearer explanation than before. I tried to reword the proposed commit log message using the description above. I feel that the title is still not optimal. If the original code used to return getenv("PWD") if the environment variable is set, and otherwise fell back to getcwd(), and the updated code tries to make sure they refer to the same directory, then "Do not trust PWD blindly" would be a good description for the fix, but the code you fixed the bug in tried not to trust PWD blindly but failed to realize that on some systems dev/ino field may be unreliable. "Do not trust st.st_ino/st.st_dev blindly" might be a better title in that sense. In any case, thanks for a fix; will queue. Author: Johannes Schindelin Date: Sat Jul 9 19:38:08 2011 +0200 Do not trust PWD blindly 10c4c88 (Allow add_path() to add non-existent directories to the path, 2008-07-21) introduced get_pwd_cwd() function in order to favor $PWD when getenv("PWD") and getcwd() refer to the same directory but are different strings (e.g. the former gives a nicer looking name via a symbolic link to an uglier looking automounted path). The function tried to determine if two directories are the same by running stat(2) on both and comparing ino/dev fields. Unfortunately, stat() does not fill any ino or dev fields in msysgit. But there is a telltale: both ino and dev are 0 when they are not filled correctly, so let's be extra cautious. This happens to fix a bug in "get-receive-pack working_directory/" when the GIT_DIR would not be set correctly due to absolute_path(".") returning the wrong value. Signed-off-by: Johannes Schindelin Acked-by: Johannes Sixt Signed-off-by: Junio C Hamano ``` ## Johannes Schindelin, 2011-07-11 17:18 Subject: Re: [PATCH] Do not trust PWD blindly Message-ID: URL: https://gitlist.dev/e/alpine.DEB.1.00.1107111917330.1534%40s15462909.onlinehome-server.info In-Reply-To: <7vbox0g3hn.fsf@alter.siamese.dyndns.org> ``` Hi, On Mon, 11 Jul 2011, Junio C Hamano wrote: > "Do not trust st.st_ino/st.st_dev blindly" might be a better title in > that sense. Maybe prefix it with "get_pwd_cwd(): "? > In any case, thanks for a fix; will queue. Thanks! Johannes ```