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Subject: Re: [nfs-utils PATCH 1/1] mount: Do not overwrite /etc/mtab if it's
 symlink
To:     Petr Vorel <petr.vorel@gmail.com>, linux-nfs@vger.kernel.org
Cc:     Joey Hess <joeyh@debian.org>, Chuck Lever <chuck.lever@oracle.com>
References: <20191120183529.29366-1-petr.vorel@gmail.com>
From:   Steve Dickson <SteveD@RedHat.com>
Message-ID: <938c3cf9-0584-d6b9-b3a1-ec12795761c5@RedHat.com>
Date:   Fri, 22 Nov 2019 10:49:18 -0500
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On 11/20/19 1:35 PM, Petr Vorel wrote:
> From: Joey Hess <joeyh@debian.org>
> 
> Some systems have /etc/mtab symlink to /proc/mounts. In that case
> mount.nfs complains:
> Can't set permissions on mtab: Operation not permitted
> 
> See https://bugs.debian.org/476577
> 
> This change makes mount.nfs handle symlinked /etc/mtab the way
> umount.nfs and util- linux handle it.
> 
> Cc: Chuck Lever <chuck.lever@oracle.com>
> Signed-off-by: Joey Hess <joeyh@debian.org>
> [ pvorel: took patch from Debian, rebased for 2.4.3-rc1 and created commit
> message. Patch is also used in Gentoo. ]
> Signed-off-by: Petr Vorel <petr.vorel@gmail.com>
Committed... (tag: nfs-utils-2-4-3-rc2)

steved.
> ---
> Hi,
> 
> if you merge, please keep Joey as the author in git :).
> 
> Kind regards,
> Petr
> 
>  utils/mount/fstab.c | 2 +-
>  utils/mount/fstab.h | 1 +
>  utils/mount/mount.c | 7 +++++++
>  3 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/utils/mount/fstab.c b/utils/mount/fstab.c
> index 8b0aaf1a..146d8f40 100644
> --- a/utils/mount/fstab.c
> +++ b/utils/mount/fstab.c
> @@ -61,7 +61,7 @@ mtab_does_not_exist(void) {
>  	return var_mtab_does_not_exist;
>  }
>  
> -static int
> +int
>  mtab_is_a_symlink(void) {
>          get_mtab_info();
>          return var_mtab_is_a_symlink;
> diff --git a/utils/mount/fstab.h b/utils/mount/fstab.h
> index 313bf9b3..8676c8c2 100644
> --- a/utils/mount/fstab.h
> +++ b/utils/mount/fstab.h
> @@ -7,6 +7,7 @@
>  #define _PATH_FSTAB "/etc/fstab"
>  #endif
>  
> +int mtab_is_a_symlink(void);
>  int mtab_is_writable(void);
>  int mtab_does_not_exist(void);
>  void reset_mtab_info(void);
> diff --git a/utils/mount/mount.c b/utils/mount/mount.c
> index 91f10877..92a0dfe4 100644
> --- a/utils/mount/mount.c
> +++ b/utils/mount/mount.c
> @@ -204,6 +204,13 @@ create_mtab (void) {
>  	int flags;
>  	mntFILE *mfp;
>  
> +	/* Avoid writing if the mtab is a symlink to /proc/mounts, since
> +	   that would create a file /proc/mounts in case the proc filesystem
> +	   is not mounted, and the fchmod below would also fail. */
> +	if (mtab_is_a_symlink()) {
> +		return EX_SUCCESS;
> +	}
> +
>  	lock_mtab();
>  
>  	mfp = nfs_setmntent (MOUNTED, "a+");
>