lkml.org 
[lkml]   [2023]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] mm/gup: Fix follow_devmap_p[mu]d() on page==NULL handling
Date
This is a bug found not by any report but only by code observations.

When GUP sees a devpmd/devpud and if page==NULL is returned, it means a
fault is probably required. Here falling through when page==NULL can cause
unexpected behavior.

Fix both cases by catching the page==NULL cases with no_page_table().

Fixes: 3565fce3a659 ("mm, x86: get_user_pages() for dax mappings")
Fixes: 080dbb618b4b ("mm/follow_page_mask: split follow_page_mask to smaller functions.")
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/gup.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/mm/gup.c b/mm/gup.c
index 231711efa390..0a5f0e91bfec 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -710,6 +710,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
spin_unlock(ptl);
if (page)
return page;
+ return no_page_table(vma, flags);
}
if (likely(!pmd_trans_huge(pmdval)))
return follow_page_pte(vma, address, pmd, flags, &ctx->pgmap);
@@ -758,6 +759,7 @@ static struct page *follow_pud_mask(struct vm_area_struct *vma,
spin_unlock(ptl);
if (page)
return page;
+ return no_page_table(vma, flags);
}
if (unlikely(pud_bad(*pud)))
return no_page_table(vma, flags);
--
2.41.0
\
 
 \ /
  Last update: 2023-11-23 19:03    [W:0.045 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site