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| author | Nick Piggin <npiggin@suse.de> | 2008-03-25 13:48:15 +0100 |
|---|---|---|
| committer | Chris Wright <chrisw@sous-sol.org> | 2008-04-18 18:53:20 -0700 |
| commit | 4193242f7ca7c2626b440fe4e9dda57f2bcf0baa (patch) | |
| tree | b34ea6ced0a0fdde18400d7a4205611f3c2677c1 | |
| parent | d4fe2bbe7a065a8aee77612356d8057239a03b84 (diff) | |
| download | kernel-common-4193242f7ca7c2626b440fe4e9dda57f2bcf0baa.tar.gz kernel-common-4193242f7ca7c2626b440fe4e9dda57f2bcf0baa.tar.bz2 kernel-common-4193242f7ca7c2626b440fe4e9dda57f2bcf0baa.zip | |
inotify: fix race
upstream commit: d599e36a9ea85432587f4550acc113cd7549d12a
There is a race between setting an inode's children's "parent watched" flag
when placing the first watch on a parent, and instantiating new children of
that parent: a child could miss having its flags set by
set_dentry_child_flags, but then inotify_d_instantiate might still see
!inotify_inode_watched.
The solution is to set_dentry_child_flags after adding the watch. Locking is
taken care of, because both set_dentry_child_flags and inotify_d_instantiate
hold dcache_lock and child->d_locks.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Robert Love <rlove@google.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Jan Kara <jack@ucw.cz>
Cc: Yan Zheng <yanzheng@21cn.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Christian Lamparter <chunkeey@web.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
| -rw-r--r-- | fs/inotify.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/fs/inotify.c b/fs/inotify.c index 2c5b92152876..b2b109bf29d6 100644 --- a/fs/inotify.c +++ b/fs/inotify.c @@ -627,6 +627,7 @@ s32 inotify_add_watch(struct inotify_handle *ih, struct inotify_watch *watch, struct inode *inode, u32 mask) { int ret = 0; + int newly_watched; /* don't allow invalid bits: we don't want flags set */ mask &= IN_ALL_EVENTS | IN_ONESHOT; @@ -653,12 +654,18 @@ s32 inotify_add_watch(struct inotify_handle *ih, struct inotify_watch *watch, */ watch->inode = igrab(inode); - if (!inotify_inode_watched(inode)) - set_dentry_child_flags(inode, 1); - /* Add the watch to the handle's and the inode's list */ + newly_watched = !inotify_inode_watched(inode); list_add(&watch->h_list, &ih->watches); list_add(&watch->i_list, &inode->inotify_watches); + /* + * Set child flags _after_ adding the watch, so there is no race + * windows where newly instantiated children could miss their parent's + * watched flag. + */ + if (newly_watched) + set_dentry_child_flags(inode, 1); + out: mutex_unlock(&ih->mutex); mutex_unlock(&inode->inotify_mutex); |