GNU bug report logs - #79072
install -d onto readonly fs prints the wrong error

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Lauri Tirkkonen <lauri <at> hacktheplanet.fi>
To: bug-coreutils <at> gnu.org
Subject: install -d onto readonly fs prints the wrong error
Date: Tue, 22 Jul 2025 13:17:30 +0900

Hi,

saw this on coreutils 9.7 on Alpine Linux, but it also reproduces on
commit 027855dcad52d718927c3405bc7d605143e2a625.

	# mount -t tmpfs -o ro none /mnt
	# ./src/ginstall -d /mnt/foo
	ginstall: cannot change permissions of ‘/mnt/foo’: No such file or directory

I would expect the error to be EROFS for creating the directory, not
changing permissions of the directory that was not able to be created.
strace confirms mkdir() returns EROFS, but install tries to open() and
stat() the not-created directory afterward.

-- 
Lauri Tirkkonen | lotheac @ IRCnet

Message #8 received at 79072 <at> debbugs.gnu.org (full text, mbox):

From: Collin Funk <collin.funk1 <at> gmail.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: Lauri Tirkkonen <lauri <at> hacktheplanet.fi>, 79072 <at> debbugs.gnu.org
Subject: Re: bug#79072: install -d onto readonly fs prints the wrong error
Date: Mon, 21 Jul 2025 23:10:09 -0700

[Message part 1 (text/plain, inline)]

Hi Lauri,

Lauri Tirkkonen via GNU coreutils Bug Reports <bug-coreutils <at> gnu.org>
writes:

> saw this on coreutils 9.7 on Alpine Linux, but it also reproduces on
> commit 027855dcad52d718927c3405bc7d605143e2a625.
>
> 	# mount -t tmpfs -o ro none /mnt
> 	# ./src/ginstall -d /mnt/foo
> 	ginstall: cannot change permissions of ‘/mnt/foo’: No such file or directory
>
> I would expect the error to be EROFS for creating the directory, not
> changing permissions of the directory that was not able to be created.
> strace confirms mkdir() returns EROFS, but install tries to open() and
> stat() the not-created directory afterward.

Thanks for the report.

It looks like the Gnulib mkdir-p module does not fail when 'mkdir' fails
with EROFS. And it looks like it has always behaved this way.

Paul, you are certainly more familiar with gnulib's mkdir-p and savewd
modules than I am. Can you check that the attached patch is correct
before I commit it?

Here is the new error based on Lauri's example:

    $ ./src/ginstall -d /mnt/foo
    ginstall: cannot create directory ‘/mnt/foo’: Read-only file system

Thanks,
Collin

[0001-mkdir-p-Diagnose-read-only-file-systems.patch (text/x-patch, attachment)]

Message #11 received at 79072 <at> debbugs.gnu.org (full text, mbox):

From: Lauri Tirkkonen <lauri <at> hacktheplanet.fi>
To: Collin Funk <collin.funk1 <at> gmail.com>
Cc: Paul Eggert <eggert <at> cs.ucla.edu>, 79072 <at> debbugs.gnu.org
Subject: Re: bug#79072: install -d onto readonly fs prints the wrong error
Date: Tue, 22 Jul 2025 15:23:16 +0900

Hi Collin,

On Mon, Jul 21 2025 23:10:09 -0700, Collin Funk wrote:
> diff --git a/lib/mkdir-p.c b/lib/mkdir-p.c
> index f5df9843e4..fc83434655 100644
> --- a/lib/mkdir-p.c
> +++ b/lib/mkdir-p.c
> @@ -182,8 +182,8 @@ make_dir_parents (char *dir,
>                      return true;
>  
>                    if (mkdir_errno == 0
> -                      || (mkdir_errno != ENOENT && make_ancestor
> -                          && errno != ENOTDIR))
> +                      || (mkdir_errno != ENOENT && mkdir_errno != EROFS
> +                          && make_ancestor && errno != ENOTDIR))
>                      {
>                        error (0, errno,
>                               _(keep_owner

Oh... looks like there is a list of errors that are reported from mkdir,
and all other errors are considered success? This being the case, even
with your patch, it's not difficult to find another scenario where we
hit the same problem (just with a different original errno). For
example, as a user without permissions to write to /:

	$ ./src/ginstall -d /foo
	ginstall: cannot change permissions of ‘/foo’: No such file or directory

-- 
Lauri Tirkkonen | lotheac @ IRCnet

Message #16 received at 79072-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Lauri Tirkkonen <lauri <at> hacktheplanet.fi>
Cc: Gnulib bugs <bug-gnulib <at> gnu.org>, 79072-done <at> debbugs.gnu.org,
 Collin Funk <collin.funk1 <at> gmail.com>
Subject: Re: bug#79072: install -d onto readonly fs prints the wrong error
Date: Tue, 22 Jul 2025 12:17:56 -0700

[Message part 1 (text/plain, inline)]

Thanks for reporting that inaccurate diagnostic. Sorry about the tricky 
code; it's a tricky situation. Looks like Collin's patch is not quite right.

I installed the attached patches into Gnulib. The first one fixes the 
two cases you mentioned, the second an unlikely bug I discovered in the 
neighborhood. Please give the patches a try. As they fix the bugs for me 
I am boldly closing the Coreutils bug report; we can reopen it if I'm wrong.

[0001-mkdir-p-better-diagnostics.patch (text/x-patch, attachment)]

[0002-mkdir-p-ENOENT-ENOTDIR-safety-and-consistency.patch (text/x-patch, attachment)]

Message #19 received at 79072 <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: 79072 <at> debbugs.gnu.org, eggert <at> cs.ucla.edu, lauri <at> hacktheplanet.fi
Subject: Re: bug#79072: install -d onto readonly fs prints the wrong error
Date: Tue, 22 Jul 2025 21:27:44 +0100

[Message part 1 (text/plain, inline)]

On 22/07/2025 20:17, Paul Eggert wrote:
> Thanks for reporting that inaccurate diagnostic. Sorry about the tricky
> code; it's a tricky situation. Looks like Collin's patch is not quite right.
> 
> I installed the attached patches into Gnulib. The first one fixes the
> two cases you mentioned, the second an unlikely bug I discovered in the
> neighborhood. Please give the patches a try. As they fix the bugs for me
> I am boldly closing the Coreutils bug report; we can reopen it if I'm wrong.

Seems to work with the attached coreutils patch
to add NEWS and a test.

thanks!
Padraig

[install-d-diag.patch (text/x-patch, attachment)]

Message #22 received at 79072 <at> debbugs.gnu.org (full text, mbox):

From: Collin Funk <collin.funk1 <at> gmail.com>
To: Pádraig Brady <P <at> draigBrady.com>
Cc: lauri <at> hacktheplanet.fi, eggert <at> cs.ucla.edu, 79072 <at> debbugs.gnu.org
Subject: Re: bug#79072: install -d onto readonly fs prints the wrong error
Date: Tue, 22 Jul 2025 15:23:06 -0700

Pádraig Brady <P <at> draigBrady.com> writes:

> Seems to work with the attached coreutils patch
> to add NEWS and a test.

Looks good, thanks.

And thanks Paul for the fix.

Collin

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