Re: [PATCH net-next v4 1/4] mm: add a signature in struct page
From: Matthew Wilcox <willy@infradead.org>
Date: 2021-05-11 13:45:56
Also in:
bpf, linux-rdma, lkml, netdev
On Tue, May 11, 2021 at 03:31:15PM +0200, Matteo Croce wrote:
quoted hunk ↗ jump to hunk
@@ -101,6 +101,7 @@ struct page { * 32-bit architectures. */ unsigned long dma_addr[2]; + unsigned long signature; }; struct { /* slab, slob and slub */ union {
No. Signature now aliases with page->mapping, which is going to go
badly wrong for drivers which map this page into userspace.
I had this as:
+ unsigned long pp_magic;
+ unsigned long xmi;
+ unsigned long _pp_mapping_pad;
unsigned long dma_addr[2];
and pp_magic needs to be set to something with bits 0&1 clear and
clearly isn't a pointer. I went with POISON_POINTER_DELTA + 0x40.