linux-kernel - Re: [PATCH 3.18 32/32] mm: larger stack guard gap, between vmas

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Date:   Tue, 20 Jun 2017 22:49:16 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Willy Tarreau <w@....eu>
Subject: Re: [PATCH 3.18 32/32] mm: larger stack guard gap, between vmas

On Mon, 19 Jun 2017, Greg Kroah-Hartman wrote:

> 3.18-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Hugh Dickins <hughd@...gle.com>
> 
> commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream.

Here's a few adjustments to the 3.18 patch: no doubt you'll have
already sorted out any build errors (and I have to confess that
I haven't even tried to build this); and the VM_WARN_ON line (as
in 4.4) only fixes a highly unlikely error; but those FOLL_MLOCK
lines in mm/gup.c were mistaken, and do need to be deleted.

Hugh

diff -purN 318n/include/linux/mm.h 318h/include/linux/mm.h
--- 318n/include/linux/mm.h	2017-06-20 16:48:54.050429965 -0700
+++ 318h/include/linux/mm.h	2017-06-20 19:13:05.842191061 -0700
@@ -1242,6 +1242,9 @@ int set_page_dirty_lock(struct page *pag
 int clear_page_dirty_for_io(struct page *page);
 int get_cmdline(struct task_struct *task, char *buffer, int buflen);
 
+extern struct task_struct *task_of_stack(struct task_struct *task,
+				struct vm_area_struct *vma, bool in_group);
+
 extern unsigned long move_page_tables(struct vm_area_struct *vma,
 		unsigned long old_addr, struct vm_area_struct *new_vma,
 		unsigned long new_addr, unsigned long len,
@@ -1897,8 +1900,9 @@ void page_cache_async_readahead(struct a
 				pgoff_t offset,
 				unsigned long size);
 
-extern unsigned long stack_guard_gap;
+unsigned long max_sane_readahead(unsigned long nr);
 
+extern unsigned long stack_guard_gap;
 /* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */
 extern int expand_stack(struct vm_area_struct *vma, unsigned long address);
 
diff -purN 318n/mm/gup.c 318h/mm/gup.c
--- 318n/mm/gup.c	2017-06-20 16:48:54.054429927 -0700
+++ 318h/mm/gup.c	2017-06-20 19:18:19.579275331 -0700
@@ -275,9 +275,6 @@ static int faultin_page(struct task_stru
 	unsigned int fault_flags = 0;
 	int ret;
 
-	/* mlock all present pages, but do not fault in new pages */
-	if (*flags & FOLL_MLOCK)
-		return -ENOENT;
 	if (*flags & FOLL_WRITE)
 		fault_flags |= FAULT_FLAG_WRITE;
 	if (nonblocking)
diff -purN 318n/mm/mmap.c 318h/mm/mmap.c
--- 318n/mm/mmap.c	2017-06-20 16:48:54.054429927 -0700
+++ 318h/mm/mmap.c	2017-06-20 19:43:16.945345744 -0700
@@ -931,7 +931,7 @@ again:			remove_next = 1 + (end > next->
 		else if (next)
 			vma_gap_update(next);
 		else
-			mm->highest_vm_end = end;
+			VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
 	}
 	if (insert && file)
 		uprobe_mmap(insert);