From: Marcos Del Sol Vives <marcos@orca.pet>
Date: Wed, 18 Sep 2024 16:38:51 GMT
Subject: RE: Permission issue in Git in DrvFs-mounted network drives
Message-ID: <19206003b1a.120df84912389761.6123103044544344593@orca.pet>
In-Reply-To: <03ed01db09e8$080cf090$1826d1b0$@nexbridge.com>




 ---- El Wed, 18 Sep 2024 18:30:05 +0200,    escribió ---- 
 > On September 18, 2024 12:16 PM, Marcos Del Sol Vives wrote:
 > >Under WSL1 (Windows Subsystem for Linux), when using a network share
 > >mounted via DrvFs, Git fails to add any files to a new or an existing repository.
 > >
 > >The reason is that Git tries to open a temporary file as with RW permissions but
 > >mode 0444, which causes WSL1 (or Samba, unsure who's here to blame) to create
 > >first an file empty with the read-only DOS attribute set that prevents any writes,
 > >and then actually trying to opening it in write mode, which of course fails.
 > >
 > >Seems to be a pretty common issue that nobody has yet reported officially, judging
 > >by the amount of posts on Stackoverflow, impacting not only WSL but also CIFS
 > >under Linux (hence why sending to this mailing list and not the Windows-specific
 > >one):
 > >
 > > - https://superuser.com/questions/681196/debugging-git-repo-permissions-on-
 > >samba-share
 > > - https://superuser.com/questions/1450094/git-on-wsl-commands-fail-despite-
 > >permissions-seeming-fine
 > > - https://superuser.com/questions/1491499/use-git-on-a-shared-drive-within-
 > >wsl
 > >
 > >As a workaround, opening the file with permissions 0600 and then using a fchmod
 > >with the final desired mode works, which is a very small change that should cause
 > >no issues under neither real Linux nor WSL:
 > >
 > >--- git-2.39.5.orig/wrapper.c
 > >+++ git-2.39.5/wrapper.c
 > >@@ -484,9 +484,11 @@ int git_mkstemps_mode(char *pattern, int
 > >             v /= num_letters;
 > >         }
 > >
 > >-        fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, mode);
 > >-        if (fd >= 0)
 > >+        fd = open(pattern, O_CREAT | O_EXCL | O_RDWR, 0600);
 > >+        if (fd >= 0) {
 > >+            fchmod(fd, mode);
 > >             return fd;
 > >+        }
 > 
 > I am not certain this is either necessary or important to platforms other than Windows.
 > The /tmp directory is often, and properly set with the sticky bit +t. This ensures that only
 > The creating user has access to the temp file regardless of create ownership or security.
 > I would prefer that this be put into a compat layer rather than made general change.
 
The temporary file is created in .git/objects/XX/tmp_obj_YYYY, not in /tmp.
As shown in the first StackExchange link, this also impacts Linux machines.

 > >         /*
 > >          * Fatal error (EPERM, ENOSPC etc).
 > >          * It doesn't make sense to loop.
 > >
 > >The WSL team at Microsoft has been already informed as well:
 > >https://github.com/microsoft/WSL/issues/12051
 > 
 >