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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Miklos Szeredi <mszeredi@redhat.com>
Subject: [PATCH 5.12 09/17] ovl: allow upperdir inside lowerdir
Date: Wed,  5 May 2021 14:06:04 +0200	[thread overview]
Message-ID: <20210505112325.259599284@linuxfoundation.org> (raw)
In-Reply-To: <20210505112324.956720416@linuxfoundation.org>

From: Miklos Szeredi <mszeredi@redhat.com>

commit 708fa01597fa002599756bf56a96d0de1677375c upstream.

Commit 146d62e5a586 ("ovl: detect overlapping layers") made sure we don't
have overlapping layers, but it also broke the arguably valid use case of

 mount -olowerdir=/,upperdir=/subdir,..

where upperdir overlaps lowerdir on the same filesystem.  This has been
causing regressions.

Revert the check, but only for the specific case where upperdir and/or
workdir are subdirectories of lowerdir.  Any other overlap (e.g. lowerdir
is subdirectory of upperdir, etc) case is crazy, so leave the check in
place for those.

Overlaps are detected at lookup time too, so reverting the mount time check
should be safe.

Fixes: 146d62e5a586 ("ovl: detect overlapping layers")
Cc: <stable@vger.kernel.org> # v5.2
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/overlayfs/super.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1826,7 +1826,8 @@ out_err:
  * - upper/work dir of any overlayfs instance
  */
 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
-			   struct dentry *dentry, const char *name)
+			   struct dentry *dentry, const char *name,
+			   bool is_lower)
 {
 	struct dentry *next = dentry, *parent;
 	int err = 0;
@@ -1838,7 +1839,7 @@ static int ovl_check_layer(struct super_
 
 	/* Walk back ancestors to root (inclusive) looking for traps */
 	while (!err && parent != next) {
-		if (ovl_lookup_trap_inode(sb, parent)) {
+		if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
 			err = -ELOOP;
 			pr_err("overlapping %s path\n", name);
 		} else if (ovl_is_inuse(parent)) {
@@ -1864,7 +1865,7 @@ static int ovl_check_overlapping_layers(
 
 	if (ovl_upper_mnt(ofs)) {
 		err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
-				      "upperdir");
+				      "upperdir", false);
 		if (err)
 			return err;
 
@@ -1875,7 +1876,8 @@ static int ovl_check_overlapping_layers(
 		 * workbasedir.  In that case, we already have their traps in
 		 * inode cache and we will catch that case on lookup.
 		 */
-		err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir");
+		err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
+				      false);
 		if (err)
 			return err;
 	}
@@ -1883,7 +1885,7 @@ static int ovl_check_overlapping_layers(
 	for (i = 1; i < ofs->numlayer; i++) {
 		err = ovl_check_layer(sb, ofs,
 				      ofs->layers[i].mnt->mnt_root,
-				      "lowerdir");
+				      "lowerdir", true);
 		if (err)
 			return err;
 	}



  parent reply	other threads:[~2021-05-05 12:10 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-05 12:05 [PATCH 5.12 00/17] 5.12.2-rc1 review Greg Kroah-Hartman
2021-05-05 12:05 ` [PATCH 5.12 01/17] mips: Do not include hi and lo in clobber list for R6 Greg Kroah-Hartman
2021-05-05 12:05 ` [PATCH 5.12 02/17] netfilter: conntrack: Make global sysctls readonly in non-init netns Greg Kroah-Hartman
2021-05-05 12:05 ` [PATCH 5.12 03/17] net: usb: ax88179_178a: initialize local variables before use Greg Kroah-Hartman
2021-05-05 12:05 ` [PATCH 5.12 04/17] drm/i915: Disable runtime power management during shutdown Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 05/17] bpf: Fix masking negation logic upon negative dst register Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 06/17] bpf: Fix leakage of uninitialized bpf stack under speculation Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 07/17] net: qrtr: Avoid potential use after free in MHI send Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 08/17] ovl: fix leaked dentry Greg Kroah-Hartman
2021-05-05 12:06 ` Greg Kroah-Hartman [this message]
2021-05-05 12:06 ` [PATCH 5.12 10/17] ALSA: usb-audio: Add MIDI quirk for Vox ToneLab EX Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 11/17] ALSA: usb-audio: Fix implicit sync clearance at stopping stream Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 12/17] USB: Add LPM quirk for Lenovo ThinkPad USB-C Dock Gen2 Ethernet Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 13/17] USB: Add reset-resume quirk for WD19s Realtek Hub Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 14/17] ASoC: ak4458: Add MODULE_DEVICE_TABLE Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 15/17] ASoC: ak5558: " Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 16/17] platform/x86: thinkpad_acpi: Correct thermal sensor allocation Greg Kroah-Hartman
2021-05-05 12:06 ` [PATCH 5.12 17/17] perf/core: Fix unconditional security_locked_down() call Greg Kroah-Hartman
2021-05-05 17:52 ` [PATCH 5.12 00/17] 5.12.2-rc1 review Fox Chen
2021-05-05 19:09 ` Naresh Kamboju
2021-05-05 19:44 ` Florian Fainelli
2021-05-06  1:59 ` Guenter Roeck

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