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authorEric Paris <eparis@redhat.com>2009-06-12 16:04:26 -0400
committerEric Paris <eparis@redhat.com>2009-06-19 12:42:48 -0400
commit528da3e9e237059a84a2625e942811cf824a6efd (patch)
tree7d3de6d5468d6835a4d81bfa1e717100dc7b71bf /fs
parent0732f87761dbe417cb6e084b712d07e879e876ef (diff)
downloadlinux-528da3e9e237059a84a2625e942811cf824a6efd.tar.gz
inotify: inotify_destroy_mark_entry could get called twice
inotify_destroy_mark_entry could get called twice for the same mark since it is called directly in inotify_rm_watch and when the mark is being destroyed for another reason. As an example assume that the file being watched was just deleted so inotify_destroy_mark_entry would get called from the path fsnotify_inoderemove() -> fsnotify_destroy_marks_by_inode() -> fsnotify_destroy_mark_entry() -> inotify_destroy_mark_entry(). If this happened at the same time as userspace tried to remove a watch via inotify_rm_watch we could attempt to remove the mark from the idr twice and could thus double dec the ref cnt and potentially could be in a use after free/double free situation. The fix is to have inotify_rm_watch use the generic recursive safe fsnotify_destroy_mark_by_entry() so we are sure the inotify_destroy_mark_entry() function can only be called one. This patch also renames the function to inotify_ingored_remove_idr() so it is clear what is actually going on in the function. Hopefully this fixes: [ 20.342058] idr_remove called for id=20 which is not allocated. [ 20.348000] Pid: 1860, comm: udevd Not tainted 2.6.30-tip #1077 [ 20.353933] Call Trace: [ 20.356410] [<ffffffff811a82b7>] idr_remove+0x115/0x18f [ 20.361737] [<ffffffff8134259d>] ? _spin_lock+0x6d/0x75 [ 20.367061] [<ffffffff8111640a>] ? inotify_destroy_mark_entry+0xa3/0xcf [ 20.373771] [<ffffffff8111641e>] inotify_destroy_mark_entry+0xb7/0xcf [ 20.380306] [<ffffffff81115913>] inotify_freeing_mark+0xe/0x10 [ 20.386238] [<ffffffff8111410d>] fsnotify_destroy_mark_by_entry+0x143/0x170 [ 20.393293] [<ffffffff811163a3>] inotify_destroy_mark_entry+0x3c/0xcf [ 20.399829] [<ffffffff811164d1>] sys_inotify_rm_watch+0x9b/0xc6 [ 20.405850] [<ffffffff8100bcdb>] system_call_fastpath+0x16/0x1b Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Eric Paris <eparis@redhat.com> Tested-by: Peter Ziljlstra <peterz@infradead.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/notify/inotify/inotify.h3
-rw-r--r--fs/notify/inotify/inotify_fsnotify.c2
-rw-r--r--fs/notify/inotify/inotify_user.c32
3 files changed, 8 insertions, 29 deletions
diff --git a/fs/notify/inotify/inotify.h b/fs/notify/inotify/inotify.h
index ea2605a58b8..f234f3a4c8c 100644
--- a/fs/notify/inotify/inotify.h
+++ b/fs/notify/inotify/inotify.h
@@ -15,7 +15,8 @@ struct inotify_inode_mark_entry {
int wd;
};
-extern void inotify_destroy_mark_entry(struct fsnotify_mark_entry *entry, struct fsnotify_group *group);
+extern void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry *entry,
+ struct fsnotify_group *group);
extern void inotify_free_event_priv(struct fsnotify_event_private_data *event_priv);
extern const struct fsnotify_ops inotify_fsnotify_ops;
diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index 7ef75b83247..47cd258fd24 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -81,7 +81,7 @@ static int inotify_handle_event(struct fsnotify_group *group, struct fsnotify_ev
static void inotify_freeing_mark(struct fsnotify_mark_entry *entry, struct fsnotify_group *group)
{
- inotify_destroy_mark_entry(entry, group);
+ inotify_ignored_and_remove_idr(entry, group);
}
static bool inotify_should_send_event(struct fsnotify_group *group, struct inode *inode, __u32 mask)
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 982a412ac5b..ff231ad2389 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -363,39 +363,17 @@ static int inotify_find_inode(const char __user *dirname, struct path *path, uns
}
/*
- * When, for whatever reason, inotify is done with a mark (or what used to be a
- * watch) we need to remove that watch from the idr and we need to send IN_IGNORED
- * for the given wd.
- *
- * There is a bit of recursion here. The loop looks like:
- * inotify_destroy_mark_entry -> fsnotify_destroy_mark_by_entry ->
- * inotify_freeing_mark -> inotify_destory_mark_entry -> restart
- * But the loop is broken in 2 places. fsnotify_destroy_mark_by_entry sets
- * entry->group = NULL before the call to inotify_freeing_mark, so the if (egroup)
- * test below will not call back to fsnotify again. But even if that test wasn't
- * there this would still be safe since fsnotify_destroy_mark_by_entry() is
- * safe from recursion.
+ * Send IN_IGNORED for this wd, remove this wd from the idr, and drop the
+ * internal reference help on the mark because it is in the idr.
*/
-void inotify_destroy_mark_entry(struct fsnotify_mark_entry *entry, struct fsnotify_group *group)
+void inotify_ignored_and_remove_idr(struct fsnotify_mark_entry *entry,
+ struct fsnotify_group *group)
{
struct inotify_inode_mark_entry *ientry;
struct inotify_event_private_data *event_priv;
struct fsnotify_event_private_data *fsn_event_priv;
- struct fsnotify_group *egroup;
struct idr *idr;
- spin_lock(&entry->lock);
- egroup = entry->group;
-
- /* if egroup we aren't really done and something might still send events
- * for this inode, on the callback we'll send the IN_IGNORED */
- if (egroup) {
- spin_unlock(&entry->lock);
- fsnotify_destroy_mark_by_entry(entry);
- return;
- }
- spin_unlock(&entry->lock);
-
ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
event_priv = kmem_cache_alloc(event_priv_cachep, GFP_KERNEL);
@@ -699,7 +677,7 @@ SYSCALL_DEFINE2(inotify_rm_watch, int, fd, __s32, wd)
fsnotify_get_mark(entry);
spin_unlock(&group->inotify_data.idr_lock);
- inotify_destroy_mark_entry(entry, group);
+ fsnotify_destroy_mark_by_entry(entry);
fsnotify_put_mark(entry);
out: