Debian Bug report logs - #836211
dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Reply or subscribe to this bug.

Toggle useless messages

Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Felipe Sateler <fsateler@debian.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Wed, 31 Aug 2016 12:16:10 -0300

Package: dpkg
Version: 1.18.10
Severity: normal

Hi,

overlayfs does not support renaming directories when the directories
live in the lower filesystem:

 * Directory renames only allowed on "pure upper" (already created on
 * upper filesystem, never copied up).  Directories which are on lower or
 * are merged may not be renamed.  For these -EXDEV is returned and
 * userspace has to deal with it.  This means, when copying up a
 * directory we can rely on it and ancestors being stable.

https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322

Unfortunately this means that dpkg fails at least in the case where a
directory is converted into a file: apt 1.3~rc2 moves
/usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to
fail when running in an overlayfs with the following error:

# dpkg -i /var/cache/apt/archives/apt_1.3~rc3_amd64.deb 
(Reading database ... 11401 files and directories currently installed.)
Preparing to unpack .../archives/apt_1.3~rc3_amd64.deb ...
Unpacking apt (1.3~rc3) over (1.3~rc2) ...
dpkg: error processing archive
/var/cache/apt/archives/apt_1.3~rc3_amd64.deb (--install):
 unable to move aside './usr/share/bug/apt' to install new version: Invalid cross-device link
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Processing triggers for libc-bin (2.23-5) ...
Errors were encountered while processing:
 /var/cache/apt/archives/apt_1.3~rc3_amd64.deb

I don't know what the correct workaround should be.

This can break pre-build upgrades in sbuild when the schroot is of
overlayfs type.

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable-debug
  APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages dpkg depends on:
ii  libbz2-1.0   1.0.6-8
ii  libc6        2.23-5
ii  liblzma5     5.1.1alpha+20120614-2.1
ii  libselinux1  2.5-3
ii  tar          1.29b-1
ii  zlib1g       1:1.2.8.dfsg-2+b1

dpkg recommends no packages.

Versions of packages dpkg suggests:
ii  apt  1.3~rc3

-- no debconf information

Message #10 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Johannes Schauer <josch@debian.org>

To: 836211@bugs.debian.org

Cc: fsateler@debian.org

Subject: Re: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Thu, 01 Sep 2016 08:59:34 +0200

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

Hi,

On Wed, 31 Aug 2016 12:16:10 -0300 Felipe Sateler <fsateler@debian.org> wrote:
> overlayfs does not support renaming directories when the directories
> live in the lower filesystem:
> 
>  * Directory renames only allowed on "pure upper" (already created on
>  * upper filesystem, never copied up).  Directories which are on lower or
>  * are merged may not be renamed.  For these -EXDEV is returned and
>  * userspace has to deal with it.  This means, when copying up a
>  * directory we can rely on it and ancestors being stable.
> 
> https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322
> 
> Unfortunately this means that dpkg fails at least in the case where a
> directory is converted into a file: apt 1.3~rc2 moves
> /usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to
> fail when running in an overlayfs with the following error:
> 
> # dpkg -i /var/cache/apt/archives/apt_1.3~rc3_amd64.deb 
> (Reading database ... 11401 files and directories currently installed.)
> Preparing to unpack .../archives/apt_1.3~rc3_amd64.deb ...
> Unpacking apt (1.3~rc3) over (1.3~rc2) ...
> dpkg: error processing archive
> /var/cache/apt/archives/apt_1.3~rc3_amd64.deb (--install):
>  unable to move aside './usr/share/bug/apt' to install new version: Invalid cross-device link
> dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
> Processing triggers for libc-bin (2.23-5) ...
> Errors were encountered while processing:
>  /var/cache/apt/archives/apt_1.3~rc3_amd64.deb
> 
> I don't know what the correct workaround should be.
> 
> This can break pre-build upgrades in sbuild when the schroot is of
> overlayfs type.

thanks for the analysis!

I just stumbled across the exact same problem with sbuild in a directory type
overlayfs schroot. My workaround: destroy the chroot (you can now use
sbuild-destroychroot) and then recreate it with sbuild-createchroot. :(

cheers, josch

[signature.asc (application/pgp-signature, inline)]

Message #15 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Felipe Sateler <fsateler@debian.org>

To: Johannes Schauer <josch@debian.org>

Cc: 836211@bugs.debian.org

Subject: Re: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Thu, 1 Sep 2016 08:19:09 -0300

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

On 1 Sep 2016 3:59 a.m., "Johannes Schauer" <josch@debian.org> wrote:
>
> Hi,
>
> On Wed, 31 Aug 2016 12:16:10 -0300 Felipe Sateler <fsateler@debian.org>
wrote:
> > overlayfs does not support renaming directories when the directories
> > live in the lower filesystem:
> >
> >  * Directory renames only allowed on "pure upper" (already created on
> >  * upper filesystem, never copied up).  Directories which are on lower
or
> >  * are merged may not be renamed.  For these -EXDEV is returned and
> >  * userspace has to deal with it.  This means, when copying up a
> >  * directory we can rely on it and ancestors being stable.
> >
> >
https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322
> >
> > Unfortunately this means that dpkg fails at least in the case where a
> > directory is converted into a file: apt 1.3~rc2 moves
> > /usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to
> > fail when running in an overlayfs with the following error:
> >
> > # dpkg -i /var/cache/apt/archives/apt_1.3~rc3_amd64.deb
> > (Reading database ... 11401 files and directories currently installed.)
> > Preparing to unpack .../archives/apt_1.3~rc3_amd64.deb ...
> > Unpacking apt (1.3~rc3) over (1.3~rc2) ...
> > dpkg: error processing archive
> > /var/cache/apt/archives/apt_1.3~rc3_amd64.deb (--install):
> >  unable to move aside './usr/share/bug/apt' to install new version:
Invalid cross-device link
> > dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
> > Processing triggers for libc-bin (2.23-5) ...
> > Errors were encountered while processing:
> >  /var/cache/apt/archives/apt_1.3~rc3_amd64.deb
> >
> > I don't know what the correct workaround should be.
> >
> > This can break pre-build upgrades in sbuild when the schroot is of
> > overlayfs type.
>
> thanks for the analysis!
>
> I just stumbled across the exact same problem with sbuild in a directory
type
> overlayfs schroot. My workaround: destroy the chroot (you can now use
> sbuild-destroychroot) and then recreate it with sbuild-createchroot. :(

You can also enter the source chroot and upgrade there, as that skips the
overlayfs setup. I used  sbuild-update and it worked OK.

I discussed this with Guillem on IRC and he doesn't think adding
workarounds for this is reasonable, and this should be fixed in overlayfs.
Assuming a directory lives in the same device as itself seems reasonable to
me, and overlayfs should try hard to pretend it does.

Saludos

[Message part 2 (text/html, inline)]

Message #20 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Raphael Hertzog <hertzog@debian.org>

To: Felipe Sateler <fsateler@debian.org>, 836211@bugs.debian.org

Cc: Miklos Szeredi <miklos@szeredi.hu>

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Fri, 2 Sep 2016 13:36:33 +0200

Hi,

On Wed, 31 Aug 2016, Felipe Sateler wrote:
> overlayfs does not support renaming directories when the directories
> live in the lower filesystem:
[...]
> Unfortunately this means that dpkg fails at least in the case where a
> directory is converted into a file: apt 1.3~rc2 moves
> /usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to

That's the change at the package level. The operation that fails
at the dpkg level is rename('/usr/share/bug/apt', '/usr/share/bug/apt.dpkg-tmp').

> fail when running in an overlayfs with the following error:
[...]
>  unable to move aside './usr/share/bug/apt' to install new version: Invalid cross-device link

I got the same failure here but I also saw similar reports in a Kali live
system where overlayfs is used for persistence (and with the upgrade
of gedit). So that error is affecting many Kali users. It's not a
very rare error (ex: https://bugs.kali.org/view.php?id=3473,
https://bugs.kali.org/view.php?id=3476,
https://bugs.kali.org/view.php?id=3361,
https://bugs.kali.org/view.php?id=3365).

I'm putting in copy the overlayfs kernel maintainer... Hello Miklos,
that restriction above (cf 
https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322)
is very problematic for us.

Do you have plans to get rid of it?

It does not seem very correct to put the burden on user-space to be aware
of overlayfs restrictions such as this one. Renaming a directory is
not something that happens often in practice in the uses cases where
we use overlayfs but it's still frequent enough to deserve better than
a EXDEV error IMO and dpkg trying to rename "foo/" into "foo.dpkg-tmp/"
is in its right to assume that this rename will not cross any device
boundary.

I'm happy to test out kernel patches if I can help you in the process
of getting a fix.

Cheers,
-- 
Raphaël Hertzog ◈ Debian Developer

Support Debian LTS: http://www.freexian.com/services/debian-lts.html
Learn to master Debian: http://debian-handbook.info/get/

Message #25 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Miklos Szeredi <miklos@szeredi.hu>

To: Raphael Hertzog <hertzog@debian.org>

Cc: Felipe Sateler <fsateler@debian.org>, 836211@bugs.debian.org, "linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Fri, 2 Sep 2016 14:30:58 +0200

On Fri, Sep 2, 2016 at 1:36 PM, Raphael Hertzog <hertzog@debian.org> wrote:
> Hi,
>
> On Wed, 31 Aug 2016, Felipe Sateler wrote:
>> overlayfs does not support renaming directories when the directories
>> live in the lower filesystem:
> [...]
>> Unfortunately this means that dpkg fails at least in the case where a
>> directory is converted into a file: apt 1.3~rc2 moves
>> /usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to
>
> That's the change at the package level. The operation that fails
> at the dpkg level is rename('/usr/share/bug/apt', '/usr/share/bug/apt.dpkg-tmp').
>
>> fail when running in an overlayfs with the following error:
> [...]
>>  unable to move aside './usr/share/bug/apt' to install new version: Invalid cross-device link
>
> I got the same failure here but I also saw similar reports in a Kali live
> system where overlayfs is used for persistence (and with the upgrade
> of gedit). So that error is affecting many Kali users. It's not a
> very rare error (ex: https://bugs.kali.org/view.php?id=3473,
> https://bugs.kali.org/view.php?id=3476,
> https://bugs.kali.org/view.php?id=3361,
> https://bugs.kali.org/view.php?id=3365).
>
> I'm putting in copy the overlayfs kernel maintainer... Hello Miklos,
> that restriction above (cf
> https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322)
> is very problematic for us.
>
> Do you have plans to get rid of it?

You are the first to report that this quirk actually causes problems
in real life.

I have plans to fix this by adding a "redirector" attribute so that
copied up directories (and perhaps files) can refer to lower directory
that is found at a different location relative to the root of the
overlay from the location of the upper directory.

Maybe an example can make this more clear:

lower/foo/bar/baz
upper/foo/bar <- whiteout
upper/moved/here <- redirects to "foo/bar"

will result in the tree:

overlay/moved/here/baz

> It does not seem very correct to put the burden on user-space to be aware
> of overlayfs restrictions such as this one. Renaming a directory is
> not something that happens often in practice in the uses cases where
> we use overlayfs but it's still frequent enough to deserve better than
> a EXDEV error IMO and dpkg trying to rename "foo/" into "foo.dpkg-tmp/"
> is in its right to assume that this rename will not cross any device
> boundary.

The EXDEV trick  just works for mv(1), hence this didn't seem to be a
big issue in practice.

Thanks,
Miklos

Message #30 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Guillem Jover <guillem@debian.org>

To: Miklos Szeredi <miklos@szeredi.hu>, 836211@bugs.debian.org

Cc: Raphael Hertzog <hertzog@debian.org>, Felipe Sateler <fsateler@debian.org>, "linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Fri, 2 Sep 2016 15:03:54 +0200

Hi!

On Fri, 2016-09-02 at 14:30:58 +0200, Miklos Szeredi wrote:
> You are the first to report that this quirk actually causes problems
> in real life.
> 
> I have plans to fix this by adding a "redirector" attribute so that
> copied up directories (and perhaps files) can refer to lower directory
> that is found at a different location relative to the root of the
> overlay from the location of the upper directory.
> 
> Maybe an example can make this more clear:
> 
> lower/foo/bar/baz
> upper/foo/bar <- whiteout
> upper/moved/here <- redirects to "foo/bar"
> 
> will result in the tree:
> 
> overlay/moved/here/baz

That'd be very much appreciated, thanks!

> > It does not seem very correct to put the burden on user-space to be aware
> > of overlayfs restrictions such as this one. Renaming a directory is
> > not something that happens often in practice in the uses cases where
> > we use overlayfs but it's still frequent enough to deserve better than
> > a EXDEV error IMO and dpkg trying to rename "foo/" into "foo.dpkg-tmp/"
> > is in its right to assume that this rename will not cross any device
> > boundary.
> 
> The EXDEV trick  just works for mv(1), hence this didn't seem to be a
> big issue in practice.

In dpkg, the directory is rename(2)d to perform an atomic temporary backup,
so that it can be rolled-back in case of errors during unpacking. Having to
possibly do a deep-copy and a deep-remove, and then trying to recover from
errors inbetween those, would be very unsatisfactory.

Thanks,
Guillem

Message #35 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Raphael Hertzog <hertzog@debian.org>

To: Felipe Sateler <fsateler@debian.org>, 836211@bugs.debian.org

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Fri, 2 Sep 2016 16:46:44 +0200

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

Hi,

On Wed, 31 Aug 2016, Felipe Sateler wrote:
> I don't know what the correct workaround should be.

Just for the record, the attached patch is what we use in Kali
to work-around this problem. It works but it's not going to be merged in
Debian because we really want a fix at the overlayfs level instead
(and this is just a hack relying on "mv" to copy the whole-directory).

I post it just in case other derivatives have a similar need.

Cheers,
-- 
Raphaël Hertzog ◈ Debian Developer

Support Debian LTS: http://www.freexian.com/services/debian-lts.html
Learn to master Debian: http://debian-handbook.info/get/

[patch (text/plain, attachment)]

Message #40 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Miklos Szeredi <miklos@szeredi.hu>

To: Guillem Jover <guillem@debian.org>, 836211@bugs.debian.org, Raphael Hertzog <hertzog@debian.org>, Felipe Sateler <fsateler@debian.org>, "linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Mon, 5 Sep 2016 10:28:59 +0200

On Fri, Sep 02, 2016 at 03:03:54PM +0200, Guillem Jover wrote:
> Hi!
> 
> On Fri, 2016-09-02 at 14:30:58 +0200, Miklos Szeredi wrote:
> > You are the first to report that this quirk actually causes problems
> > in real life.
> > 
> > I have plans to fix this by adding a "redirector" attribute so that
> > copied up directories (and perhaps files) can refer to lower directory
> > that is found at a different location relative to the root of the
> > overlay from the location of the upper directory.
> > 
> > Maybe an example can make this more clear:
> > 
> > lower/foo/bar/baz
> > upper/foo/bar <- whiteout
> > upper/moved/here <- redirects to "foo/bar"
> > 
> > will result in the tree:
> > 
> > overlay/moved/here/baz
> 
> That'd be very much appreciated, thanks!

Toy patch attached.  Passes minimal test.

It does not deal with multi-layer setups when one of the lower layers was
previously an upper layer (generally overlayfs does support this, so this patch
will need to deal with that case).

You can help by

 - review it
 - improve it
 - test it
 - break it
 - write test cases in xfstests

Thanks,
Miklos

---
 fs/overlayfs/dir.c       |   42 ++++++++++++++++++++--
 fs/overlayfs/overlayfs.h |    1 
 fs/overlayfs/super.c     |   89 +++++++++++++++++++++++++++++++++++++++++------
 3 files changed, 119 insertions(+), 13 deletions(-)

--- a/fs/overlayfs/dir.c
+++ b/fs/overlayfs/dir.c
@@ -764,6 +764,31 @@ static int ovl_rmdir(struct inode *dir,
 	return ovl_do_remove(dentry, true);
 }
 
+static bool ovl_can_move(struct dentry *dentry, enum ovl_path_type type)
+{
+//	return !d_is_dir(dentry) || !OVL_TYPE_MERGE_OR_LOWER(type);
+	return true;
+}
+
+static int ovl_set_redirect(struct dentry *dentry)
+{
+	char *buf = __getname();
+	char *path;
+	int err;
+
+	if (!buf)
+		return -ENOMEM;
+
+	path = dentry_path_raw(dentry, buf, PATH_MAX);
+
+	printk(KERN_WARNING "redirect: <%s>\n", path);
+	err = ovl_do_setxattr(ovl_dentry_upper(dentry), OVL_XATTR_REDIRECT,
+			      path, strlen(path), 0);
+	__putname(buf);
+
+	return err;
+}
+
 static int ovl_rename2(struct inode *olddir, struct dentry *old,
 		       struct inode *newdir, struct dentry *new,
 		       unsigned int flags)
@@ -798,7 +823,7 @@ static int ovl_rename2(struct inode *old
 	/* Don't copy up directory trees */
 	old_type = ovl_path_type(old);
 	err = -EXDEV;
-	if (OVL_TYPE_MERGE_OR_LOWER(old_type) && is_dir)
+	if (!ovl_can_move(old, old_type))
 		goto out;
 
 	if (new->d_inode) {
@@ -811,7 +836,7 @@ static int ovl_rename2(struct inode *old
 
 		new_type = ovl_path_type(new);
 		err = -EXDEV;
-		if (!overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir)
+		if (!overwrite && !ovl_can_move(new, new_type))
 			goto out;
 
 		err = 0;
@@ -883,7 +908,6 @@ static int ovl_rename2(struct inode *old
 
 	trap = lock_rename(new_upperdir, old_upperdir);
 
-
 	olddentry = lookup_one_len(old->d_name.name, old_upperdir,
 				   old->d_name.len);
 	err = PTR_ERR(olddentry);
@@ -920,11 +944,23 @@ static int ovl_rename2(struct inode *old
 	if (newdentry == trap)
 		goto out_dput;
 
+	printk(KERN_WARNING "is_dir: %i, old_opaque: %i, old_type: %i\n",
+	       is_dir, old_opaque, old_type);
+	if (is_dir && OVL_TYPE_MERGE_OR_LOWER(old_type)) {
+		err = ovl_set_redirect(old);
+		if (err)
+			goto out_dput;
+	}
 	if (is_dir && !old_opaque && new_opaque) {
 		err = ovl_set_opaque(olddentry);
 		if (err)
 			goto out_dput;
 	}
+	if (!overwrite && new_is_dir && OVL_TYPE_MERGE_OR_LOWER(new_type)) {
+		err = ovl_set_redirect(new);
+		if (err)
+			goto out_dput;
+	}
 	if (!overwrite && new_is_dir && old_opaque && !new_opaque) {
 		err = ovl_set_opaque(newdentry);
 		if (err)
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -26,6 +26,7 @@ enum ovl_path_type {
 
 #define OVL_XATTR_PREFIX XATTR_TRUSTED_PREFIX "overlay."
 #define OVL_XATTR_OPAQUE OVL_XATTR_PREFIX "opaque"
+#define OVL_XATTR_REDIRECT OVL_XATTR_PREFIX "redirect"
 
 #define OVL_ISUPPER_MASK 1UL
 
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -285,6 +285,33 @@ static bool ovl_is_opaquedir(struct dent
 	return false;
 }
 
+static int ovl_check_redirect(struct dentry *dentry, char **bufp)
+{
+	struct inode *inode = dentry->d_inode;
+	int res;
+
+	if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
+		return false;
+
+	res = inode->i_op->getxattr(dentry, inode, OVL_XATTR_REDIRECT, NULL, 0);
+	if (res > 0) {
+		char *buf = kzalloc(res + 1, GFP_KERNEL);
+
+		if (!buf)
+			return -ENOMEM;
+
+		res = inode->i_op->getxattr(dentry, inode, OVL_XATTR_REDIRECT,
+					    buf, res);
+		if (res < 0)
+			return res;
+
+		kfree(*bufp);
+		*bufp = buf;
+	}
+
+	return 0;
+}
+
 static void ovl_dentry_release(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;
@@ -465,6 +492,9 @@ int ovl_path_next(int idx, struct dentry
 	return (idx < oe->numlower) ? idx + 1 : -1;
 }
 
+extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
+			   const char *, unsigned int, struct path *);
+
 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			  unsigned int flags)
 {
@@ -478,6 +508,7 @@ struct dentry *ovl_lookup(struct inode *
 	struct dentry *this, *prev = NULL;
 	unsigned int i;
 	int err;
+	char *redirect = NULL;
 
 	upperdir = ovl_upperdentry_dereference(poe);
 	if (upperdir) {
@@ -498,11 +529,18 @@ struct dentry *ovl_lookup(struct inode *
 				upperopaque = true;
 			} else if (poe->numlower && ovl_is_opaquedir(this)) {
 				upperopaque = true;
+			} else if (d_is_dir(this)) {
+				err = ovl_check_redirect(this, &redirect);
+				if (err)
+					goto out;
 			}
 		}
 		upperdentry = prev = this;
 	}
 
+	if (redirect)
+		poe = dentry->d_sb->s_root->d_fsdata;
+
 	if (!upperopaque && poe->numlower) {
 		err = -ENOMEM;
 		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
@@ -514,16 +552,45 @@ struct dentry *ovl_lookup(struct inode *
 		bool opaque = false;
 		struct path lowerpath = poe->lowerstack[i];
 
-		this = ovl_lookup_real(dentry->d_sb,
-				       lowerpath.dentry, &dentry->d_name);
-		err = PTR_ERR(this);
-		if (IS_ERR(this)) {
-			/*
-			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
-			 */
-			if (err == -ENAMETOOLONG && (upperdentry || ctr))
-				continue;
-			goto out_put;
+		if (!redirect) {
+			this = ovl_lookup_real(dentry->d_sb,
+					       lowerpath.dentry, &dentry->d_name);
+			err = PTR_ERR(this);
+			if (IS_ERR(this)) {
+				/*
+				 * If it's positive, then treat ENAMETOOLONG as ENOENT.
+				 */
+				if (err == -ENAMETOOLONG && (upperdentry || ctr))
+					continue;
+				goto out_put;
+			}
+		} else {
+			struct path thispath;
+
+			err = vfs_path_lookup(lowerpath.dentry, lowerpath.mnt,
+					      redirect, 0, &thispath);
+
+			if (err) {
+				if (err == -ENOENT)
+					this = NULL;
+				else if (err == -ENAMETOOLONG)
+					this = NULL;
+			} else {
+				this = thispath.dentry;
+				mntput(thispath.mnt);
+				if (err == -ENOENT) {
+					dput(this);
+					this = NULL;
+				} else if (!this->d_inode) {
+					dput(this);
+					this = NULL;
+				} else if (ovl_dentry_weird(this)) {
+					dput(this);
+					err = -EREMOTE;
+				}
+			}
+			if (err)
+				goto out_put;
 		}
 		if (!this)
 			continue;
@@ -592,6 +659,7 @@ struct dentry *ovl_lookup(struct inode *
 	oe->__upperdentry = upperdentry;
 	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
 	kfree(stack);
+	kfree(redirect);
 	dentry->d_fsdata = oe;
 	d_add(dentry, inode);
 
@@ -606,6 +674,7 @@ struct dentry *ovl_lookup(struct inode *
 out_put_upper:
 	dput(upperdentry);
 out:
+	kfree(redirect);
 	return ERR_PTR(err);
 }
 

Message #45 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Guillem Jover <guillem@debian.org>

To: Felipe Sateler <fsateler@debian.org>, 836211@bugs.debian.org

Cc: linux@packages.debian.org

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Sat, 17 Sep 2016 17:36:09 +0200

Control: reassign -1 linux
Control: affects -1 dpkg

Hi!

[ Reassigning to linux, where this can be fixed. Upstream has provided
  a preliminary patch to this bug report, which might need testing and
  perhaps some polishing? Trimmed irrelevant information. ]

On Wed, 2016-08-31 at 12:16:10 -0300, Felipe Sateler wrote:
> Package: dpkg
> Version: 1.18.10
> Severity: normal

> overlayfs does not support renaming directories when the directories
> live in the lower filesystem:
> 
>  * Directory renames only allowed on "pure upper" (already created on
>  * upper filesystem, never copied up).  Directories which are on lower or
>  * are merged may not be renamed.  For these -EXDEV is returned and
>  * userspace has to deal with it.  This means, when copying up a
>  * directory we can rely on it and ancestors being stable.
> 
> https://github.com/torvalds/linux/blob/v4.8-rc2/fs/overlayfs/copy_up.c#L318-L322
> 
> Unfortunately this means that dpkg fails at least in the case where a
> directory is converted into a file: apt 1.3~rc2 moves
> /usr/share/bug/apt/script to /usr/share/bug/apt . This causes dpkg to
> fail when running in an overlayfs with the following error:
> 
> # dpkg -i /var/cache/apt/archives/apt_1.3~rc3_amd64.deb 
> (Reading database ... 11401 files and directories currently installed.)
> Preparing to unpack .../archives/apt_1.3~rc3_amd64.deb ...
> Unpacking apt (1.3~rc3) over (1.3~rc2) ...
> dpkg: error processing archive
> /var/cache/apt/archives/apt_1.3~rc3_amd64.deb (--install):
>  unable to move aside './usr/share/bug/apt' to install new version: Invalid cross-device link
> dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
> Processing triggers for libc-bin (2.23-5) ...
> Errors were encountered while processing:
>  /var/cache/apt/archives/apt_1.3~rc3_amd64.deb
> 
> I don't know what the correct workaround should be.
> 
> This can break pre-build upgrades in sbuild when the schroot is of
> overlayfs type.

> -- System Information:
> Debian Release: stretch/sid
>   APT prefers unstable-debug
>   APT policy: (500, 'unstable-debug'), (500, 'unstable'), (1, 'experimental-debug'), (1, 'experimental')
> Architecture: amd64 (x86_64)
> Foreign Architectures: i386
> 
> Kernel: Linux 4.6.0-1-amd64 (SMP w/4 CPU cores)

Thanks,
Guillem

Message #62 received at 836211-done@bugs.debian.org (full text, mbox, reply):

From: Raphael Hertzog <hertzog@debian.org>

To: Guillem Jover <guillem@debian.org>

Cc: Felipe Sateler <fsateler@debian.org>, 836211-done@bugs.debian.org

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Fri, 25 Aug 2017 21:34:32 +0200

Version: 4.10.0-1~exp1

On Sat, 17 Sep 2016, Guillem Jover wrote:
> [ Reassigning to linux, where this can be fixed. Upstream has provided
>   a preliminary patch to this bug report, which might need testing and
>   perhaps some polishing? Trimmed irrelevant information. ]

I verified today that the issue is gone with Linux 4.12 and apparently
the appropriate patches have been merged for Linux 4.10 already (merged by
linus in commit ff0f962ca3c38239b299a70e7eea27abfbb979c3).

So I'm closing this bug.

Cheers,
-- 
Raphaël Hertzog ◈ Debian Developer

Support Debian LTS: https://www.freexian.com/services/debian-lts.html
Learn to master Debian: https://debian-handbook.info/get/

Message #67 received at 836211@bugs.debian.org (full text, mbox, reply):

From: Raphael Hertzog <hertzog@debian.org>

To: Guillem Jover <guillem@debian.org>

Cc: Felipe Sateler <fsateler@debian.org>, 836211@bugs.debian.org

Subject: Re: Bug#836211: dpkg: Cannot upgrade some packages on overlayfs: Invalid cross-device link

Date: Mon, 4 Sep 2017 15:01:26 +0200

Control: reopen -1
Control: notfixed -1 4.10.0-1~exp1
Control: found -1 4.12.6-1

On Fri, 25 Aug 2017, Raphael Hertzog wrote:
> I verified today that the issue is gone with Linux 4.12 and apparently
> the appropriate patches have been merged for Linux 4.10 already (merged by
> linus in commit ff0f962ca3c38239b299a70e7eea27abfbb979c3).

I don't know how I did my check last time, but I was wrong. The changes
merged above fixed issues about tools being confused with the unexpected
st_dev values on files but they did not fix the fact that overlayfs
might return EXDEV when renaming a directory that is part of the lower
layer.

So I'm opening the bug again.

Cheers,
-- 
Raphaël Hertzog ◈ Debian Developer

Support Debian LTS: https://www.freexian.com/services/debian-lts.html
Learn to master Debian: https://debian-handbook.info/get/

Send a report that this bug log contains spam.