Re: [PATCH] Improve the filemode trustability check
- From
Junio C Hamano <gitster@pobox.com>
- Date
- Nov 19, 2014, 18:58 UTC
- Message-ID
- <xmqqegszrp8x.fsf@gitster.dls.corp.google.com>
- In-Reply-To
- <546CB2F8.7040501@web.de>
Torsten Bögershausen <tboegi@web.de> writes:
Show 17 quoted lines
> Some file systems do not support the executable bit:
> a) The user executable bit is always 0, e.g. VFAT mounted with -onoexec
> b) The user executable bit is always 1, e.g. cifs mounted with -ofile_mode=0755
> c) There are system where user executable bit is 1 even if it should be 0
> like b), but the file mode can be maintained locally. chmod -x changes the
> file mode from 0766 to 0666, until the file system is unmounted and
> remounted and the file mode is 0766 again.
> This been observed when a Windows machine with NTFS exports a share to
> Mac OS X via smb or afp.
>
> Case a) and b) are handled by the current code.
> Case c) qualifies as "non trustable executable bit" and core.filemode
> should be false, but this is not done.
>
> Solution:
> Detect when ".git/config" has the user executable bit set after
> creat(".git/config", 0666) and set core.filemode to false.The readers have been following along a nicely flowing prose; let them keep going by dropping that abrupt "Solution:" line and instead doing s/to false./to false to solve this./ or something like that.
The change does not seem to match the above design of the solution, though. We've run stat(path, &st1), and I would have expected from the description that (st1.st_mode & S_IXUSR) without any chmod() would be the "does the file have executable bit without us asking?" Either the explanation or the code is wrong. I cannot tell which.
Show 27 quoted lines
> Signed-off-by: Torsten Bögershausen <tboegi@web.de>
> ---
>
> This should go on top of "mh/config-flip-xbit-back-after-checking"
>
> Michael, thanks for the test case.
> And no, I havent seen any systems with behaving like d)
>
> builtin/init-db.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/builtin/init-db.c b/builtin/init-db.c
> index aab44d2..9b50dde 100644
> --- a/builtin/init-db.c
> +++ b/builtin/init-db.c
> @@ -252,10 +252,10 @@ static int create_default_files(const char *template_path)
> filemode = TEST_FILEMODE;
> if (TEST_FILEMODE && !lstat(path, &st1)) {
> struct stat st2;
> - filemode = (!chmod(path, st1.st_mode ^ S_IXUSR) &&
> + filemode = (!chmod(path, st1.st_mode | S_IXUSR) &&
> !lstat(path, &st2) &&
> st1.st_mode != st2.st_mode &&
> - !chmod(path, st1.st_mode));
> + !chmod(path, st1.st_mode & (~S_IXUSR)));
> }
> git_config_set("core.filemode", filemode ? "true" : "false");