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autofs-5.1.4 - set bind mount as propagation slave
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From: Ian Kent <raven@themaw.net>
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When using a multi-mount with mount targets that are on the
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local machine and resulting bind mounts are made to a file
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system that is mount propagation shared (such as the root
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file system on systemd managed systems) the autofs offset
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mount triggers made within the bind mount will be propagated
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back to the target file system.
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When this happens the target of the offset (the unwanted
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propagated mount) is itself an autofs trigger mount and
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accessing the path results in a deadlock.
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In order for these multi-mounts to function properly in this
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case bind mounts that contain mount triggers must be set to
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propagation slave or private so the backward propagation
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doesn't occur.
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Signed-off-by: Ian Kent <raven@themaw.net>
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---
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CHANGELOG | 1 +
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modules/mount_bind.c | 16 +++++++++++++++-
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2 files changed, 16 insertions(+), 1 deletion(-)
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--- autofs-5.1.4.orig/CHANGELOG
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+++ autofs-5.1.4/CHANGELOG
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@@ -30,6 +30,7 @@ xx/xx/2018 autofs-5.1.5
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- fix program usage message.
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- fix update_negative_cache() map source usage.
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- mark removed cache entry negative.
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+- set bind mount as propagation slave.
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19/12/2017 autofs-5.1.4
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- fix spec file url.
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--- autofs-5.1.4.orig/modules/mount_bind.c
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+++ autofs-5.1.4/modules/mount_bind.c
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@@ -20,6 +20,7 @@
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#include <sys/param.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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+#include <sys/mount.h>
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#define MODULE_MOUNT
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#include "automount.h"
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@@ -183,8 +184,21 @@ int mount_mount(struct autofs_point *ap,
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debug(ap->logopt,
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MODPREFIX "mounted %s type %s on %s",
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what, fstype, fullpath);
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- return 0;
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}
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+
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+ /* The bind mount has succeeded but if the target
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+ * mount is propagation shared propagation of child
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+ * mounts (autofs offset mounts for example) back to
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+ * the target of the bind mount must be avoided or
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+ * autofs trigger mounts will deadlock.
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+ */
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+ err = mount(NULL, fullpath, NULL, MS_SLAVE, NULL);
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+ if (err)
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+ warn(ap->logopt,
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+ "failed to set propagation type for %s",
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+ fullpath);
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+
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+ return 0;
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} else {
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char *cp;
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char basepath[PATH_MAX];
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