On Mon, Nov 25, 2024 at 12:05 AM Mateusz Guzik <mjguzik@xxxxxxxxx> wrote:
> Looks like this is a recurring topic?
>
> Until the day comes when someone has way too much time on their hands
> and patches it up (even that may encounter resistance though), I do
> think it would make sense to nicely write it down somewhere so for
> easy reference -- maybe as a comment above getattr and note around
> other places like the timespec helpers to read that.
>
I'll add personally I was concerned with uid:gid pairs vs chown --
after all you can read an incorrect pair after getting unlucky enough.
Again one has to really try to run into it though.
So how about something like this:
diff --git a/fs/stat.c b/fs/stat.c
index 0870e969a8a0..302586d6afae 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -78,6 +78,11 @@ EXPORT_SYMBOL(fill_mg_cmtime);
* take care to map the inode according to @idmap before filling in the
* uid and gid filds. On non-idmapped mounts or if permission checking is to be
* performed on the raw inode simply pass @nop_mnt_idmap.
+ *
+ * DONTFIXME: no effort is put into ensuring a consistent snapshot of the
+ * metadata read below. For example a call racing against parallel setattr()
+ * can end up with a mixture of old and new attributes. This is not considered
+ * enough to warrant fixing.
*/
void generic_fillattr(struct mnt_idmap *idmap, u32 request_mask,
struct inode *inode, struct kstat *stat)
not an actual patch submission, any party is free to take the comment
and tweak in whatever capacity without credit.
What I am after here is preventing more people from spotting the
problem and thinking it is new.
--
Mateusz Guzik <mjguzik gmail.com>
