Re: [PATCH 01/16] mm: use untagged_addr() for get_user_pages_fast addresses
From: Jason Gunthorpe <jgg@ziepe.ca>
Date: 2019-06-21 13:39:15
Also in:
linux-mips, linux-mm, linux-sh, lkml, sparclinux
Subsystem:
memory management, memory management - gup (get user pages), the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
On Tue, Jun 11, 2019 at 04:40:47PM +0200, Christoph Hellwig wrote:
quoted hunk ↗ jump to hunk
This will allow sparc64 to override its ADI tags for get_user_pages and get_user_pages_fast. Signed-off-by: Christoph Hellwig <hch@lst.de> mm/gup.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/mm/gup.c b/mm/gup.c index ddde097cf9e4..6bb521db67ec 100644 +++ b/mm/gup.c@@ -2146,7 +2146,7 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, unsigned long flags; int nr = 0; - start &= PAGE_MASK; + start = untagged_addr(start) & PAGE_MASK; len = (unsigned long) nr_pages << PAGE_SHIFT; end = start + len;
Hmm, this function, and the other, goes on to do:
if (unlikely(!access_ok((void __user *)start, len)))
return 0;
and I thought that access_ok takes in the tagged pointer?
How about re-order it a bit?
diff --git a/mm/gup.c b/mm/gup.c
index ddde097cf9e410..f48747ced4723b 100644
--- a/mm/gup.c
+++ b/mm/gup.c@@ -2148,11 +2148,12 @@ int __get_user_pages_fast(unsigned long start, int nr_pages, int write, start &= PAGE_MASK; len = (unsigned long) nr_pages << PAGE_SHIFT; - end = start + len; - if (unlikely(!access_ok((void __user *)start, len))) return 0; + start = untagged_ptr(start); + end = start + len; + /* * Disable interrupts. We use the nested form as we can already have * interrupts disabled by get_futex_key.