The patch titled
inotify: fix race
has been added to the -mm tree. Its filename is
inotify-fix-race.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: inotify: fix race
From: Nick Piggin <npiggin@xxxxxxx>
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@xxxxxxx>
Cc: Robert Love <rlove@xxxxxxxxxx>
Cc: John McCutchan <ttb@xxxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxx>
Cc: Yan Zheng <yanzheng@xxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/inotify.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff -puN fs/inotify.c~inotify-fix-race fs/inotify.c
--- a/fs/inotify.c~inotify-fix-race
+++ a/fs/inotify.c
@@ -627,6 +627,7 @@ s32 inotify_add_watch(struct inotify_han
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_han
*/
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);
_
Patches currently in -mm which might be from npiggin@xxxxxxx are
git-jfs.patch
nfs-use-gfp_nofs-preloads-for-radix-tree-insertion.patch
slub-use-non-atomic-bit-unlock.patch
radix-tree-avoid-atomic-allocations-for-preloaded-insertions.patch
mm-dont-allow-ioremapping-of-ranges-larger-than-vmalloc-space.patch
vt-bitlock-fix.patch
radix_treeh-trivial-comment-correction.patch
inotify-fix-race.patch
inotify-remove-debug-code.patch
reiser4.patch
-
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