On Mon, Apr 27, 2020 at 10:08:22AM -0400, Waiman Long wrote:
> In a couple of places in the slub memory allocator, the code uses
> "s->offset" as a check to see if the free pointer is put right after the
> object. That check is no longer true with commit 3202fa62fb43 ("slub:
> relocate freelist pointer to middle of object").
>
> As a result, echoing "1" into the validate sysfs file, e.g. of dentry,
> may cause a bunch of "Freepointer corrupt" error reports like the
> following to appear with the system in panic afterwards.
>
> [ 38.579769] =============================================================================
> [ 38.580845] BUG dentry(666:pmcd.service) (Tainted: G B): Freepointer corrupt
> [ 38.581948] -----------------------------------------------------------------------------
>
> To fix it, use the check "s->offset == s->inuse" in the new helper
> function freeptr_after_object() instead. Also add another helper function
> get_info_end() to return the end of info block (inuse + free pointer
> if not overlapping with object).
>
> Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object")
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Reviewed-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
