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| author | Lino Sanfilippo <LinoSanfilippo@gmx.de> | 2010-11-09 18:18:16 +0100 |
|---|---|---|
| committer | Eric Paris <eparis@redhat.com> | 2010-12-07 16:14:21 -0500 |
| commit | fa218ab98c31eeacd12b89501e6b99d146ea56cc (patch) | |
| tree | 789e0f922fbb30844a89a4aaf707c01991c74ea3 /fs | |
| parent | b1085ba80cd2784400a7beec3fda5099198ed01c (diff) | |
| download | linux-fa218ab98c31eeacd12b89501e6b99d146ea56cc.tar.gz linux-fa218ab98c31eeacd12b89501e6b99d146ea56cc.tar.bz2 linux-fa218ab98c31eeacd12b89501e6b99d146ea56cc.zip | |
fanotify: correct broken ref counting in case adding a mark failed
If adding a mount or inode mark failed fanotify_free_mark() is called explicitly.
But at this time the mark has already been put into the destroy list of the
fsnotify_mark kernel thread. If the thread is too slow it will try to decrease
the reference of a mark, that has already been freed by fanotify_free_mark().
(If its fast enough it will only decrease the marks ref counter from 2 to 1 - note
that the counter has been increased to 2 in add_mark() - which has practically no
effect.)
This patch fixes the ref counting by not calling free_mark() explicitly, but
decreasing the ref counter and rely on the fsnotify_mark thread to cleanup in
case adding the mark has failed.
Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Eric Paris <eparis@redhat.com>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 31 |
1 files changed, 14 insertions, 17 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 045c0794d435..c0ca1fa1550c 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -594,11 +594,10 @@ static int fanotify_add_vfsmount_mark(struct fsnotify_group *group, { struct fsnotify_mark *fsn_mark; __u32 added; + int ret = 0; fsn_mark = fsnotify_find_vfsmount_mark(group, mnt); if (!fsn_mark) { - int ret; - if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks) return -ENOSPC; @@ -608,17 +607,16 @@ static int fanotify_add_vfsmount_mark(struct fsnotify_group *group, fsnotify_init_mark(fsn_mark, fanotify_free_mark); ret = fsnotify_add_mark(fsn_mark, group, NULL, mnt, 0); - if (ret) { - fanotify_free_mark(fsn_mark); - return ret; - } + if (ret) + goto err; } added = fanotify_mark_add_to_mask(fsn_mark, mask, flags); - fsnotify_put_mark(fsn_mark); + if (added & ~mnt->mnt_fsnotify_mask) fsnotify_recalc_vfsmount_mask(mnt); - - return 0; +err: + fsnotify_put_mark(fsn_mark); + return ret; } static int fanotify_add_inode_mark(struct fsnotify_group *group, @@ -627,6 +625,7 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group, { struct fsnotify_mark *fsn_mark; __u32 added; + int ret = 0; pr_debug("%s: group=%p inode=%p\n", __func__, group, inode); @@ -642,8 +641,6 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group, fsn_mark = fsnotify_find_inode_mark(group, inode); if (!fsn_mark) { - int ret; - if (atomic_read(&group->num_marks) > group->fanotify_data.max_marks) return -ENOSPC; @@ -653,16 +650,16 @@ static int fanotify_add_inode_mark(struct fsnotify_group *group, fsnotify_init_mark(fsn_mark, fanotify_free_mark); ret = fsnotify_add_mark(fsn_mark, group, inode, NULL, 0); - if (ret) { - fanotify_free_mark(fsn_mark); - return ret; - } + if (ret) + goto err; } added = fanotify_mark_add_to_mask(fsn_mark, mask, flags); - fsnotify_put_mark(fsn_mark); + if (added & ~inode->i_fsnotify_mask) fsnotify_recalc_inode_mask(inode); - return 0; +err: + fsnotify_put_mark(fsn_mark); + return ret; } /* fanotify syscalls */ |