The patch titled
fs/namespace.c: bound mount propagation fix
has been removed from the -mm tree. Its filename was
fs-namespacec-bound-mount-propagation-fix.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: fs/namespace.c: bound mount propagation fix
From: Roman Borisov <ext-roman.borisov@xxxxxxxxx>
This issue was discovered by users of busybox. And the bug is actual for
busybox users, I don't know how it affects others. Apparently, mount is
called with and without MS_SILENT, and this affects mount() behaviour.
But MS_SILENT is only supposed to affect kernel logging verbosity.
The following script was run in an empty test directory:
mkdir -p mount.dir mount.shared1 mount.shared2
touch mount.dir/a mount.dir/b
mount -vv --bind mount.shared1 mount.shared1
mount -vv --make-rshared mount.shared1
mount -vv --bind mount.shared2 mount.shared2
mount -vv --make-rshared mount.shared2
mount -vv --bind mount.shared2 mount.shared1
mount -vv --bind mount.dir mount.shared2
ls -R mount.dir mount.shared1 mount.shared2
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
rm -f mount.dir/a mount.dir/b mount.dir/c
rmdir mount.dir mount.shared1 mount.shared2
mount -vv was used to show the mount() call arguments and result.
Output shows that flag argument has 0x00008000 = MS_SILENT bit:
mount: mount('mount.shared1','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared1','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared2','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared2','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('mount.dir','mount.shared2','(null)',0x00009000,'(null)'):0
mount.dir:
a
b
mount.shared1:
mount.shared2:
a
b
After adding --loud option to remove MS_SILENT bit from just one mount cmd:
mkdir -p mount.dir mount.shared1 mount.shared2
touch mount.dir/a mount.dir/b
mount -vv --bind mount.shared1 mount.shared1 2>&1
mount -vv --make-rshared mount.shared1 2>&1
mount -vv --bind mount.shared2 mount.shared2 2>&1
mount -vv --loud --make-rshared mount.shared2 2>&1 # <-HERE
mount -vv --bind mount.shared2 mount.shared1 2>&1
mount -vv --bind mount.dir mount.shared2 2>&1
ls -R mount.dir mount.shared1 mount.shared2 2>&1
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
umount mount.dir mount.shared1 mount.shared2 2>/dev/null
rm -f mount.dir/a mount.dir/b mount.dir/c
rmdir mount.dir mount.shared1 mount.shared2
The result is different now - look closely at mount.shared1 directory listing.
Now it does show files 'a' and 'b':
mount: mount('mount.shared1','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared1','',0x0010c000,''):0
mount: mount('mount.shared2','mount.shared2','(null)',0x00009000,'(null)'):0
mount: mount('','mount.shared2','',0x00104000,''):0
mount: mount('mount.shared2','mount.shared1','(null)',0x00009000,'(null)'):0
mount: mount('mount.dir','mount.shared2','(null)',0x00009000,'(null)'):0
mount.dir:
a
b
mount.shared1:
a
b
mount.shared2:
a
b
The analysis shows that MS_SILENT flag which is ON by default in any
busybox-> mount operations cames to flags_to_propagation_type function and
causes the error return while is_power_of_2 checking because the function
expects only one bit set. This doesn't allow to do busybox->mount with
any --make-[r]shared, --make-[r]private etc options.
Moreover, the recently added flags_to_propagation_type() function doesn't
allow us to do such operations as --make-[r]private --make-[r]shared etc.
when MS_SILENT is on. The idea or clearing the MS_SILENT flag came from
to Denys Vlasenko.
Signed-off-by: Roman Borisov <ext-roman.borisov@xxxxxxxxx>
Reported-by: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
Cc: Chuck Ebbert <cebbert@xxxxxxxxxx>
Cc: Alexander Shishkin <virtuoso@xxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN fs/namespace.c~fs-namespacec-bound-mount-propagation-fix fs/namespace.c
--- a/fs/namespace.c~fs-namespacec-bound-mount-propagation-fix
+++ a/fs/namespace.c
@@ -1695,7 +1695,7 @@ static int graft_tree(struct vfsmount *m
static int flags_to_propagation_type(int flags)
{
- int type = flags & ~MS_REC;
+ int type = flags & ~(MS_REC | MS_SILENT);
/* Fail if any non-propagation flags are set */
if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
_
Patches currently in -mm which might be from ext-roman.borisov@xxxxxxxxx are
origin.patch
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