From 9f7fe1b83fcc508dc3e05815d03dbbb752a1cfba Mon Sep 17 00:00:00 2001

From: Karel Zak <kzak@redhat.com>

Date: Fri, 1 Jun 2018 12:16:19 +0200

Subject: [PATCH 63/63] libmount: improve MS_REC usage

libmount allows to split one library (mount(8)) call to multiple mount(2)

syscalls, for example

   --rbind --make-rslave

in this case we have to be careful with MS_REC because the flag is

applied to multiple operations.

 # strace -e mount mount --rbind --make-rslave /mnt/A /mnt/B

Old version:

 mount("/mnt/A", "/mnt/B", 0x13ecac0, MS_MGC_VAL|MS_BIND, NULL) = 0

 mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0

Fixed version:

 mount("/mnt/A", "/mnt/B", 0x1f22ac0, MS_MGC_VAL|MS_BIND|MS_REC, NULL) = 0

 mount("none", "/mnt/B", NULL, MS_REC|MS_SLAVE, NULL) = 0

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1946921

Upstream: http://github.com/karelzak/util-linux/commit/816773b475900909d42c2c8282a6ac50252cac22

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 libmount/src/context.c       |  5 +++++

 libmount/src/context_mount.c | 25 ++++++++++++++++++++++---

 libmount/src/optstr.c        |  9 ++++++---

 3 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/libmount/src/context.c b/libmount/src/context.c

index e7f1ee934..8e00b75a9 100644

--- a/libmount/src/context.c

+++ b/libmount/src/context.c

@@ -1375,6 +1375,11 @@ struct libmnt_lock *mnt_context_get_lock(struct libmnt_context *cxt)

  *

  * both of these calls have the same effect.

  *

+ * Be careful if you want to use MS_REC flag -- in this case the bit is applied

+ * to all bind/slave/etc. options. If you want to mix more propadation flags

+ * and/or bind, move operations than it's better to specify mount options by

+ * strings.

+ *

  * Returns: 0 on success, negative number in case of error.

  */

 int mnt_context_set_mflags(struct libmnt_context *cxt, unsigned long flags)

diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c

index b88e60507..a8e84127c 100644

--- a/libmount/src/context_mount.c

+++ b/libmount/src/context_mount.c

@@ -73,6 +73,7 @@ static int init_propagation(struct libmnt_context *cxt)

 	char *opts = (char *) mnt_fs_get_vfs_options(cxt->fs);

 	size_t namesz;

 	struct libmnt_optmap const *maps[1];

+	int rec_count = 0;

 	if (!opts)

 		return 0;

@@ -86,9 +87,19 @@ static int init_propagation(struct libmnt_context *cxt)

 		struct libmnt_addmount *ad;

 		int rc;

-		if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent)

-		    || !ent

-		    || !(ent->id & MS_PROPAGATION))

+		if (!mnt_optmap_get_entry(maps, 1, name, namesz, &ent) || !ent)

+			continue;

+

+		DBG(CXT, ul_debugobj(cxt, " checking %s", ent->name));

+

+		/* Note that MS_REC may be used for more flags, so we have to keep

+		 * track about number of recursive options to keep the MS_REC in the

+		 * mountflags if necessary.

+		 */

+		if (ent->id & MS_REC)

+			rec_count++;

+

+		if (!(ent->id & MS_PROPAGATION))

 			continue;

 		ad = mnt_new_addmount();

@@ -96,13 +107,21 @@ static int init_propagation(struct libmnt_context *cxt)

 			return -ENOMEM;

 		ad->mountflags = ent->id;

+		DBG(CXT, ul_debugobj(cxt, " adding extra mount(2) call for %s", ent->name));

 		rc = mnt_context_append_additional_mount(cxt, ad);

 		if (rc)

 			return rc;

+		DBG(CXT, ul_debugobj(cxt, " removing %s from primary mount(2) call", ent->name));

 		cxt->mountflags &= ~ent->id;

+

+		if (ent->id & MS_REC)

+			rec_count--;

 	}

+	if (rec_count)

+		cxt->mountflags |= MS_REC;

+

 	return 0;

 }

diff --git a/libmount/src/optstr.c b/libmount/src/optstr.c

index 8248f0dee..cc077ffd9 100644

--- a/libmount/src/optstr.c

+++ b/libmount/src/optstr.c

@@ -800,14 +800,17 @@ int mnt_optstr_apply_flags(char **optstr, unsigned long flags,

 					if (rc)

 						goto err;

 				}

-				if (!(ent->mask & MNT_INVERT))

+				if (!(ent->mask & MNT_INVERT)) {

 					fl &= ~ent->id;

+					if (ent->id & MS_REC)

+						fl |= MS_REC;

+				}

 			}

 		}

 	}

-	/* add missing options */

-	if (fl) {

+	/* add missing options (but ignore fl if contains MS_REC only) */

+	if (fl && fl != MS_REC) {

 		const struct libmnt_optmap *ent;

 		char *p;

-- 

2.31.1