The patch titled
Subject: fsnotify: fix oops in fsnotify_clear_marks_by_group_flags()
has been added to the -mm tree. Its filename is
fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Jan Kara <[email protected]>
Subject: fsnotify: fix oops in fsnotify_clear_marks_by_group_flags()
fsnotify_clear_marks_by_group_flags() can race with
fsnotify_destroy_marks() so when fsnotify_destroy_mark_locked() drops
mark_mutex, a mark from the list iterated by
fsnotify_clear_marks_by_group_flags() can be freed and we dereference free
memory in the loop there.
Fix the problem by keeping mark_mutex held in
fsnotify_destroy_mark_locked(). The reason why we drop that mutex is that
we need to call a ->freeing_mark() callback which may acquire mark_mutex
again. To avoid this and similar lock inversion issues, we move the call
to ->freeing_mark() callback to the kthread destroying the mark.
Signed-off-by: Jan Kara <[email protected]>
Reported-by: Ashish Sangwan <[email protected]>
Suggested-by: Lino Sanfilippo <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
fs/notify/mark.c | 34 ++++++++++++++--------------------
1 file changed, 14 insertions(+), 20 deletions(-)
diff -puN
fs/notify/mark.c~fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags
fs/notify/mark.c
--- a/fs/notify/mark.c~fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags
+++ a/fs/notify/mark.c
@@ -152,31 +152,15 @@ void fsnotify_destroy_mark_locked(struct
BUG();
list_del_init(&mark->g_list);
-
spin_unlock(&mark->lock);
if (inode && (mark->flags & FSNOTIFY_MARK_FLAG_OBJECT_PINNED))
iput(inode);
- /* release lock temporarily */
- mutex_unlock(&group->mark_mutex);
spin_lock(&destroy_lock);
list_add(&mark->g_list, &destroy_list);
spin_unlock(&destroy_lock);
wake_up(&destroy_waitq);
- /*
- * We don't necessarily have a ref on mark from caller so the above
destroy
- * may have actually freed it, unless this group provides a
'freeing_mark'
- * function which must be holding a reference.
- */
-
- /*
- * Some groups like to know that marks are being freed. This is a
- * callback to the group function to let it know that this mark
- * is being freed.
- */
- if (group->ops->freeing_mark)
- group->ops->freeing_mark(mark, group);
/*
* __fsnotify_update_child_dentry_flags(inode);
@@ -191,8 +175,6 @@ void fsnotify_destroy_mark_locked(struct
*/
atomic_dec(&group->num_marks);
-
- mutex_lock_nested(&group->mark_mutex, SINGLE_DEPTH_NESTING);
}
void fsnotify_destroy_mark(struct fsnotify_mark *mark,
@@ -205,7 +187,10 @@ void fsnotify_destroy_mark(struct fsnoti
/*
* Destroy all marks in the given list. The marks must be already detached from
- * the original inode / vfsmount.
+ * the original inode / vfsmount. Note that we can race with
+ * fsnotify_clear_marks_by_group_flags(). However we hold a reference to each
+ * mark so they won't get freed from under us and nobody else touches our
+ * free_list list_head.
*/
void fsnotify_destroy_marks(struct list_head *to_free)
{
@@ -406,7 +391,7 @@ struct fsnotify_mark *fsnotify_find_mark
}
/*
- * clear any marks in a group in which mark->flags & flags is true
+ * Clear any marks in a group in which mark->flags & flags is true.
*/
void fsnotify_clear_marks_by_group_flags(struct fsnotify_group *group,
unsigned int flags)
@@ -460,6 +445,7 @@ static int fsnotify_mark_destroy(void *i
{
struct fsnotify_mark *mark, *next;
struct list_head private_destroy_list;
+ struct fsnotify_group *group;
for (;;) {
spin_lock(&destroy_lock);
@@ -471,6 +457,14 @@ static int fsnotify_mark_destroy(void *i
list_for_each_entry_safe(mark, next, &private_destroy_list,
g_list) {
list_del_init(&mark->g_list);
+ group = mark->group;
+ /*
+ * Some groups like to know that marks are being freed.
+ * This is a callback to the group function to let it
+ * know that this mark is being freed.
+ */
+ if (group && group->ops->freeing_mark)
+ group->ops->freeing_mark(mark, group);
fsnotify_put_mark(mark);
}
_
Patches currently in -mm which might be from [email protected] are
fsnotify-fix-oops-in-fsnotify_clear_marks_by_group_flags.patch
fsnotify-fix-check-in-inotify-fdinfo-printing.patch
fs-ext4-fsyncc-generic_file_fsync-call-based-on-barrier-flag.patch
thp-vma_adjust_trans_huge-adjust-file-backed-vma-too.patch
dax-move-dax-related-functions-to-a-new-header.patch
thp-prepare-for-dax-huge-pages.patch
mm-add-a-pmd_fault-handler.patch
mm-export-various-functions-for-the-benefit-of-dax.patch
mm-add-vmf_insert_pfn_pmd.patch
dax-add-huge-page-fault-support.patch
ext2-huge-page-fault-support.patch
ext4-huge-page-fault-support.patch
xfs-huge-page-fault-support.patch
fs-mpagec-forgotten-write_sync-in-case-of-data-integrity-write.patch
kstrto-accept-0-for-signed-conversion.patch
add-parse_integer-replacement-for-simple_strto.patch
parse_integer-add-runtime-testsuite.patch
parse_integer-convert-ext2-ext3-ext4.patch
mm-add-strictlimit-knob-v2.patch
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