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author | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-18 11:20:31 -0400 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-18 11:20:31 -0400 |
commit | 8f502d5b9e3362971f58dad5d468f070340336e1 (patch) | |
tree | fa819b5acdfc43c01e3696991ffe90836f265a34 /include/linux/mount.h | |
parent | 06a60deca87dba8e2c186ea7f12ea87d6785188e (diff) | |
parent | e0c9c0afd2fc958ffa34b697972721d81df8a56f (diff) |
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull usernamespace mount fixes from Eric Biederman:
"Way back in October Andrey Vagin reported that umount(MNT_DETACH)
could be used to defeat MNT_LOCKED. As I worked to fix this I
discovered that combined with mount propagation and an appropriate
selection of shared subtrees a reference to a directory on an
unmounted filesystem is not necessary.
That MNT_DETACH is allowed in user namespace in a form that can break
MNT_LOCKED comes from my early misunderstanding what MNT_DETACH does.
To avoid breaking existing userspace the conflict between MNT_DETACH
and MNT_LOCKED is fixed by leaving mounts that are locked to their
parents in the mount hash table until the last reference goes away.
While investigating this issue I also found an issue with
__detach_mounts. The code was unnecessarily and incorrectly
triggering mount propagation. Resulting in too many mounts going away
when a directory is deleted, and too many cpu cycles are burned while
doing that.
Looking some more I realized that __detach_mounts by only keeping
mounts connected that were MNT_LOCKED it had the potential to still
leak information so I tweaked the code to keep everything locked
together that possibly could be.
This code was almost ready last cycle but Al invented fs_pin which
slightly simplifies this code but required rewrites and retesting, and
I have not been in top form for a while so it took me a while to get
all of that done. Similiarly this pull request is late because I have
been feeling absolutely miserable all week.
The issue of being able to escape a bind mount has not yet been
addressed, as the fixes are not yet mature"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
mnt: Update detach_mounts to leave mounts connected
mnt: Fix the error check in __detach_mounts
mnt: Honor MNT_LOCKED when detaching mounts
fs_pin: Allow for the possibility that m_list or s_list go unused.
mnt: Factor umount_mnt from umount_tree
mnt: Factor out unhash_mnt from detach_mnt and umount_tree
mnt: Fail collect_mounts when applied to unmounted mounts
mnt: Don't propagate unmounts to locked mounts
mnt: On an unmount propagate clearing of MNT_LOCKED
mnt: Delay removal from the mount hash.
mnt: Add MNT_UMOUNT flag
mnt: In umount_tree reuse mnt_list instead of mnt_hash
mnt: Don't propagate umounts in __detach_mounts
mnt: Improve the umount_tree flags
mnt: Use hlist_move_list in namespace_unlock
Diffstat (limited to 'include/linux/mount.h')
-rw-r--r-- | include/linux/mount.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/mount.h b/include/linux/mount.h index bca086d62b1a..f822c3c11377 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -61,6 +61,7 @@ struct mnt_namespace; #define MNT_DOOMED 0x1000000 #define MNT_SYNC_UMOUNT 0x2000000 #define MNT_MARKED 0x4000000 +#define MNT_UMOUNT 0x8000000 struct vfsmount { struct dentry *mnt_root; /* root of the mounted tree */ |