Backport fix for CVE-2017-1000364 to linux-yocto-4.8

Backport of upstream fixes from 4.9 kernel branch to linux-yocto:
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.34&id=cfc0eb403816c5c4f9667d959de5e22789b5421e
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.34&id=5d10ad6297260e9b85e7645ee544a6115bb229e4
- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=v4.9.34&id=ce7fe8595902c3f03ef528c2dc1928b3f4b67fcf

Change-Id: I5bedd3af344b32b410bb7d59448710799143107d
Bug-AGL: SPEC-705
Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/9853
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
Reviewed-by: Stéphane Desneux <stephane.desneux@iot.bzh>

1 files changed, 899 insertions, 0 deletions

diff --git a/meta-agl-bsp/recipes-kernel/linux/linux-yocto/4.8-0001-SEC-Backport-Fix-CVE-2017-1000364-through-backport.patch b/meta-agl-bsp/recipes-kernel/linux/linux-yocto/4.8-0001-SEC-Backport-Fix-CVE-2017-1000364-through-backport.patch
new file mode 100644
index 000000000..f68a3747b
--- /dev/null
+++ b/meta-agl-bsp/recipes-kernel/linux/linux-yocto/4.8-0001-SEC-Backport-Fix-CVE-2017-1000364-through-backport.patch
@@ -0,0 +1,899 @@
+From 75349cc7326dd2aa645bf21fe65a40c68b386c29 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Jan-Simon=20M=C3=B6ller?= <jsmoeller@linuxfoundation.org>
+Date: Wed, 28 Jun 2017 00:35:18 +0200
+Subject: [PATCH] [SEC][Backport] Fix CVE-2017-1000364 through backport
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Fix CVE-2017-1000364 through backport of upstream patches (from 4.9 branch):
+- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.9.y&id=cfc0eb403816c5c4f9667d959de5e22789b5421e
+- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.9.y&id=5d10ad6297260e9b85e7645ee544a6115bb229e4
+- https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?h=linux-4.9.y&id=ce7fe8595902c3f03ef528c2dc1928b3f4b67fcf
+
+Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>
+---
+ Documentation/kernel-parameters.txt |   7 ++
+ arch/arc/mm/mmap.c                  |   2 +-
+ arch/arm/mm/mmap.c                  |   4 +-
+ arch/frv/mm/elf-fdpic.c             |   2 +-
+ arch/mips/mm/mmap.c                 |   2 +-
+ arch/parisc/kernel/sys_parisc.c     |  15 ++--
+ arch/powerpc/mm/hugetlbpage-radix.c |   2 +-
+ arch/powerpc/mm/mmap.c              |   4 +-
+ arch/powerpc/mm/slice.c             |   2 +-
+ arch/s390/mm/mmap.c                 |   4 +-
+ arch/sh/mm/mmap.c                   |   4 +-
+ arch/sparc/kernel/sys_sparc_64.c    |   4 +-
+ arch/sparc/mm/hugetlbpage.c         |   2 +-
+ arch/tile/mm/hugetlbpage.c          |   2 +-
+ arch/x86/kernel/sys_x86_64.c        |   4 +-
+ arch/x86/mm/hugetlbpage.c           |   2 +-
+ arch/xtensa/kernel/syscall.c        |   2 +-
+ fs/hugetlbfs/inode.c                |   2 +-
+ fs/proc/task_mmu.c                  |   4 -
+ include/linux/mm.h                  |  53 ++++++------
+ mm/gup.c                            |   5 --
+ mm/memory.c                         |  38 ---------
+ mm/mmap.c                           | 158 ++++++++++++++++++++++--------------
+ 23 files changed, 159 insertions(+), 165 deletions(-)
+
+diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
+index 46726d4899fe..c1980b5c6a15 100644
+--- a/Documentation/kernel-parameters.txt
++++ b/Documentation/kernel-parameters.txt
+@@ -3852,6 +3852,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
+ 	spia_pedr=
+ 	spia_peddr=
+ 
++	stack_guard_gap=	[MM]
++			override the default stack gap protection. The value
++			is in page units and it defines how many pages prior
++			to (for stacks growing down) resp. after (for stacks
++			growing up) the main stack are reserved for no other
++			mapping. Default value is 256 pages.
++
+ 	stacktrace	[FTRACE]
+ 			Enabled the stack tracer on boot up.
+ 
+diff --git a/arch/arc/mm/mmap.c b/arch/arc/mm/mmap.c
+index 2e06d56e987b..cf4ae6958240 100644
+--- a/arch/arc/mm/mmap.c
++++ b/arch/arc/mm/mmap.c
+@@ -64,7 +64,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
+index 66353caa35b9..641334ebf46d 100644
+--- a/arch/arm/mm/mmap.c
++++ b/arch/arm/mm/mmap.c
+@@ -89,7 +89,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -140,7 +140,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 			addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-				(!vma || addr + len <= vma->vm_start))
++				(!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/frv/mm/elf-fdpic.c b/arch/frv/mm/elf-fdpic.c
+index 836f14707a62..efa59f1f8022 100644
+--- a/arch/frv/mm/elf-fdpic.c
++++ b/arch/frv/mm/elf-fdpic.c
+@@ -74,7 +74,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(current->mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			goto success;
+ 	}
+ 
+diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
+index 353037699512..c5fdea5debe5 100644
+--- a/arch/mips/mm/mmap.c
++++ b/arch/mips/mm/mmap.c
+@@ -92,7 +92,7 @@ static unsigned long arch_get_unmapped_area_common(struct file *filp,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/parisc/kernel/sys_parisc.c b/arch/parisc/kernel/sys_parisc.c
+index 0a393a04e891..1d7691fa8ab2 100644
+--- a/arch/parisc/kernel/sys_parisc.c
++++ b/arch/parisc/kernel/sys_parisc.c
+@@ -88,7 +88,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		unsigned long len, unsigned long pgoff, unsigned long flags)
+ {
+ 	struct mm_struct *mm = current->mm;
+-	struct vm_area_struct *vma;
++	struct vm_area_struct *vma, *prev;
+ 	unsigned long task_size = TASK_SIZE;
+ 	int do_color_align, last_mmap;
+ 	struct vm_unmapped_area_info info;
+@@ -115,9 +115,10 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		else
+ 			addr = PAGE_ALIGN(addr);
+ 
+-		vma = find_vma(mm, addr);
++		vma = find_vma_prev(mm, addr, &prev);
+ 		if (task_size - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)) &&
++		    (!prev || addr >= vm_end_gap(prev)))
+ 			goto found_addr;
+ 	}
+ 
+@@ -141,7 +142,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 			  const unsigned long len, const unsigned long pgoff,
+ 			  const unsigned long flags)
+ {
+-	struct vm_area_struct *vma;
++	struct vm_area_struct *vma, *prev;
+ 	struct mm_struct *mm = current->mm;
+ 	unsigned long addr = addr0;
+ 	int do_color_align, last_mmap;
+@@ -175,9 +176,11 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 			addr = COLOR_ALIGN(addr, last_mmap, pgoff);
+ 		else
+ 			addr = PAGE_ALIGN(addr);
+-		vma = find_vma(mm, addr);
++
++		vma = find_vma_prev(mm, addr, &prev);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)) &&
++		    (!prev || addr >= vm_end_gap(prev)))
+ 			goto found_addr;
+ 	}
+ 
+diff --git a/arch/powerpc/mm/hugetlbpage-radix.c b/arch/powerpc/mm/hugetlbpage-radix.c
+index 35254a678456..a2b2d97f7eda 100644
+--- a/arch/powerpc/mm/hugetlbpage-radix.c
++++ b/arch/powerpc/mm/hugetlbpage-radix.c
+@@ -65,7 +65,7 @@ radix__hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 		addr = ALIGN(addr, huge_page_size(h));
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 	/*
+diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
+index 2f1e44362198..5bc2845cddf4 100644
+--- a/arch/powerpc/mm/mmap.c
++++ b/arch/powerpc/mm/mmap.c
+@@ -106,7 +106,7 @@ radix__arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -142,7 +142,7 @@ radix__arch_get_unmapped_area_topdown(struct file *filp,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-				(!vma || addr + len <= vma->vm_start))
++				(!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
+index 2b27458902ee..c4d5c9c61e0f 100644
+--- a/arch/powerpc/mm/slice.c
++++ b/arch/powerpc/mm/slice.c
+@@ -105,7 +105,7 @@ static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
+ 	if ((mm->task_size - len) < addr)
+ 		return 0;
+ 	vma = find_vma(mm, addr);
+-	return (!vma || (addr + len) <= vma->vm_start);
++	return (!vma || (addr + len) <= vm_start_gap(vma));
+ }
+ 
+ static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice)
+diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
+index eb9df2822da1..812368f274c9 100644
+--- a/arch/s390/mm/mmap.c
++++ b/arch/s390/mm/mmap.c
+@@ -98,7 +98,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -136,7 +136,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-				(!vma || addr + len <= vma->vm_start))
++				(!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/sh/mm/mmap.c b/arch/sh/mm/mmap.c
+index 6777177807c2..7df7d5944188 100644
+--- a/arch/sh/mm/mmap.c
++++ b/arch/sh/mm/mmap.c
+@@ -63,7 +63,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -113,7 +113,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
+index fe8b8ee8e660..02e05e221b94 100644
+--- a/arch/sparc/kernel/sys_sparc_64.c
++++ b/arch/sparc/kernel/sys_sparc_64.c
+@@ -118,7 +118,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (task_size - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -181,7 +181,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 
+ 		vma = find_vma(mm, addr);
+ 		if (task_size - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
+index 988acc8b1b80..58cde8d9be8a 100644
+--- a/arch/sparc/mm/hugetlbpage.c
++++ b/arch/sparc/mm/hugetlbpage.c
+@@ -116,7 +116,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 		addr = ALIGN(addr, HPAGE_SIZE);
+ 		vma = find_vma(mm, addr);
+ 		if (task_size - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 	if (mm->get_unmapped_area == arch_get_unmapped_area)
+diff --git a/arch/tile/mm/hugetlbpage.c b/arch/tile/mm/hugetlbpage.c
+index 77ceaa343fce..67508b249ede 100644
+--- a/arch/tile/mm/hugetlbpage.c
++++ b/arch/tile/mm/hugetlbpage.c
+@@ -232,7 +232,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 		addr = ALIGN(addr, huge_page_size(h));
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 	if (current->mm->get_unmapped_area == arch_get_unmapped_area)
+diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
+index 10e0272d789a..136ad7c1ce7b 100644
+--- a/arch/x86/kernel/sys_x86_64.c
++++ b/arch/x86/kernel/sys_x86_64.c
+@@ -143,7 +143,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (end - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+@@ -186,7 +186,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 		addr = PAGE_ALIGN(addr);
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-				(!vma || addr + len <= vma->vm_start))
++				(!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
+index 2ae8584b44c7..fe342e8ed529 100644
+--- a/arch/x86/mm/hugetlbpage.c
++++ b/arch/x86/mm/hugetlbpage.c
+@@ -144,7 +144,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 		addr = ALIGN(addr, huge_page_size(h));
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 	if (mm->get_unmapped_area == arch_get_unmapped_area)
+diff --git a/arch/xtensa/kernel/syscall.c b/arch/xtensa/kernel/syscall.c
+index 83cf49685373..3aaaae18417c 100644
+--- a/arch/xtensa/kernel/syscall.c
++++ b/arch/xtensa/kernel/syscall.c
+@@ -87,7 +87,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		/* At this point:  (!vmm || addr < vmm->vm_end). */
+ 		if (TASK_SIZE - len < addr)
+ 			return -ENOMEM;
+-		if (!vmm || addr + len <= vmm->vm_start)
++		if (!vmm || addr + len <= vm_start_gap(vmm))
+ 			return addr;
+ 		addr = vmm->vm_end;
+ 		if (flags & MAP_SHARED)
+diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
+index 4ea71eba40a5..aac9114728c3 100644
+--- a/fs/hugetlbfs/inode.c
++++ b/fs/hugetlbfs/inode.c
+@@ -191,7 +191,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 		addr = ALIGN(addr, huge_page_size(h));
+ 		vma = find_vma(mm, addr);
+ 		if (TASK_SIZE - len >= addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)))
+ 			return addr;
+ 	}
+ 
+diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
+index 2750949397eb..5feada822930 100644
+--- a/fs/proc/task_mmu.c
++++ b/fs/proc/task_mmu.c
+@@ -309,11 +309,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
+ 
+ 	/* We don't show the stack guard page in /proc/maps */
+ 	start = vma->vm_start;
+-	if (stack_guard_page_start(vma, start))
+-		start += PAGE_SIZE;
+ 	end = vma->vm_end;
+-	if (stack_guard_page_end(vma, end))
+-		end -= PAGE_SIZE;
+ 
+ 	seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
+ 	seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
+diff --git a/include/linux/mm.h b/include/linux/mm.h
+index 582d30baaa86..31206cc2e99c 100644
+--- a/include/linux/mm.h
++++ b/include/linux/mm.h
+@@ -1392,39 +1392,11 @@ int clear_page_dirty_for_io(struct page *page);
+ 
+ int get_cmdline(struct task_struct *task, char *buffer, int buflen);
+ 
+-/* Is the vma a continuation of the stack vma above it? */
+-static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr)
+-{
+-	return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN);
+-}
+-
+ static inline bool vma_is_anonymous(struct vm_area_struct *vma)
+ {
+ 	return !vma->vm_ops;
+ }
+ 
+-static inline int stack_guard_page_start(struct vm_area_struct *vma,
+-					     unsigned long addr)
+-{
+-	return (vma->vm_flags & VM_GROWSDOWN) &&
+-		(vma->vm_start == addr) &&
+-		!vma_growsdown(vma->vm_prev, addr);
+-}
+-
+-/* Is the vma a continuation of the stack vma below it? */
+-static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr)
+-{
+-	return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP);
+-}
+-
+-static inline int stack_guard_page_end(struct vm_area_struct *vma,
+-					   unsigned long addr)
+-{
+-	return (vma->vm_flags & VM_GROWSUP) &&
+-		(vma->vm_end == addr) &&
+-		!vma_growsup(vma->vm_next, addr);
+-}
+-
+ int vma_is_stack_for_task(struct vm_area_struct *vma, struct task_struct *t);
+ 
+ extern unsigned long move_page_tables(struct vm_area_struct *vma,
+@@ -2153,6 +2125,7 @@ void page_cache_async_readahead(struct address_space *mapping,
+ 				pgoff_t offset,
+ 				unsigned long size);
+ 
++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);
+ 
+@@ -2181,6 +2154,30 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
+ 	return vma;
+ }
+ 
++static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
++{
++	unsigned long vm_start = vma->vm_start;
++
++	if (vma->vm_flags & VM_GROWSDOWN) {
++		vm_start -= stack_guard_gap;
++		if (vm_start > vma->vm_start)
++			vm_start = 0;
++	}
++	return vm_start;
++}
++
++static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
++{
++	unsigned long vm_end = vma->vm_end;
++
++	if (vma->vm_flags & VM_GROWSUP) {
++		vm_end += stack_guard_gap;
++		if (vm_end < vma->vm_end)
++			vm_end = -PAGE_SIZE;
++	}
++	return vm_end;
++}
++
+ static inline unsigned long vma_pages(struct vm_area_struct *vma)
+ {
+ 	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+diff --git a/mm/gup.c b/mm/gup.c
+index 22cc22e7432f..4b3723734623 100644
+--- a/mm/gup.c
++++ b/mm/gup.c
+@@ -370,11 +370,6 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
+ 	/* mlock all present pages, but do not fault in new pages */
+ 	if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
+ 		return -ENOENT;
+-	/* For mm_populate(), just skip the stack guard page. */
+-	if ((*flags & FOLL_POPULATE) &&
+-			(stack_guard_page_start(vma, address) ||
+-			 stack_guard_page_end(vma, address + PAGE_SIZE)))
+-		return -ENOENT;
+ 	if (*flags & FOLL_WRITE)
+ 		fault_flags |= FAULT_FLAG_WRITE;
+ 	if (*flags & FOLL_REMOTE)
+diff --git a/mm/memory.c b/mm/memory.c
+index 45f39f391cc2..527ef7841146 100644
+--- a/mm/memory.c
++++ b/mm/memory.c
+@@ -2695,40 +2695,6 @@ out_release:
+ }
+ 
+ /*
+- * This is like a special single-page "expand_{down|up}wards()",
+- * except we must first make sure that 'address{-|+}PAGE_SIZE'
+- * doesn't hit another vma.
+- */
+-static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address)
+-{
+-	address &= PAGE_MASK;
+-	if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) {
+-		struct vm_area_struct *prev = vma->vm_prev;
+-
+-		/*
+-		 * Is there a mapping abutting this one below?
+-		 *
+-		 * That's only ok if it's the same stack mapping
+-		 * that has gotten split..
+-		 */
+-		if (prev && prev->vm_end == address)
+-			return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM;
+-
+-		return expand_downwards(vma, address - PAGE_SIZE);
+-	}
+-	if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) {
+-		struct vm_area_struct *next = vma->vm_next;
+-
+-		/* As VM_GROWSDOWN but s/below/above/ */
+-		if (next && next->vm_start == address + PAGE_SIZE)
+-			return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM;
+-
+-		return expand_upwards(vma, address + PAGE_SIZE);
+-	}
+-	return 0;
+-}
+-
+-/*
+  * We enter with non-exclusive mmap_sem (to exclude vma changes,
+  * but allow concurrent faults), and pte mapped but not yet locked.
+  * We return with mmap_sem still held, but pte unmapped and unlocked.
+@@ -2744,10 +2710,6 @@ static int do_anonymous_page(struct fault_env *fe)
+ 	if (vma->vm_flags & VM_SHARED)
+ 		return VM_FAULT_SIGBUS;
+ 
+-	/* Check if we need to add a guard page to the stack */
+-	if (check_stack_guard_page(vma, fe->address) < 0)
+-		return VM_FAULT_SIGSEGV;
+-
+ 	/*
+ 	 * Use pte_alloc() instead of pte_alloc_map().  We can't run
+ 	 * pte_offset_map() on pmds where a huge pmd might be created
+diff --git a/mm/mmap.c b/mm/mmap.c
+index f3ebc5a54367..e1c1eb4b3942 100644
+--- a/mm/mmap.c
++++ b/mm/mmap.c
+@@ -176,6 +176,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
+ 	unsigned long retval;
+ 	unsigned long newbrk, oldbrk;
+ 	struct mm_struct *mm = current->mm;
++	struct vm_area_struct *next;
+ 	unsigned long min_brk;
+ 	bool populate;
+ 
+@@ -221,7 +222,8 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
+ 	}
+ 
+ 	/* Check against existing mmap mappings. */
+-	if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE))
++	next = find_vma(mm, oldbrk);
++	if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
+ 		goto out;
+ 
+ 	/* Ok, looks good - let it rip. */
+@@ -244,10 +246,22 @@ out:
+ 
+ static long vma_compute_subtree_gap(struct vm_area_struct *vma)
+ {
+-	unsigned long max, subtree_gap;
+-	max = vma->vm_start;
+-	if (vma->vm_prev)
+-		max -= vma->vm_prev->vm_end;
++	unsigned long max, prev_end, subtree_gap;
++
++	/*
++	 * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
++	 * allow two stack_guard_gaps between them here, and when choosing
++	 * an unmapped area; whereas when expanding we only require one.
++	 * That's a little inconsistent, but keeps the code here simpler.
++	 */
++	max = vm_start_gap(vma);
++	if (vma->vm_prev) {
++		prev_end = vm_end_gap(vma->vm_prev);
++		if (max > prev_end)
++			max -= prev_end;
++		else
++			max = 0;
++	}
+ 	if (vma->vm_rb.rb_left) {
+ 		subtree_gap = rb_entry(vma->vm_rb.rb_left,
+ 				struct vm_area_struct, vm_rb)->rb_subtree_gap;
+@@ -343,7 +357,7 @@ static void validate_mm(struct mm_struct *mm)
+ 			anon_vma_unlock_read(anon_vma);
+ 		}
+ 
+-		highest_address = vma->vm_end;
++		highest_address = vm_end_gap(vma);
+ 		vma = vma->vm_next;
+ 		i++;
+ 	}
+@@ -512,7 +526,7 @@ void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
+ 	if (vma->vm_next)
+ 		vma_gap_update(vma->vm_next);
+ 	else
+-		mm->highest_vm_end = vma->vm_end;
++		mm->highest_vm_end = vm_end_gap(vma);
+ 
+ 	/*
+ 	 * vma->vm_prev wasn't known when we followed the rbtree to find the
+@@ -765,7 +779,7 @@ again:
+ 			vma_gap_update(vma);
+ 		if (end_changed) {
+ 			if (!next)
+-				mm->highest_vm_end = end;
++				mm->highest_vm_end = vm_end_gap(vma);
+ 			else if (!adjust_next)
+ 				vma_gap_update(next);
+ 		}
+@@ -1630,7 +1644,7 @@ unsigned long unmapped_area(struct vm_unmapped_area_info *info)
+ 
+ 	while (true) {
+ 		/* Visit left subtree if it looks promising */
+-		gap_end = vma->vm_start;
++		gap_end = vm_start_gap(vma);
+ 		if (gap_end >= low_limit && vma->vm_rb.rb_left) {
+ 			struct vm_area_struct *left =
+ 				rb_entry(vma->vm_rb.rb_left,
+@@ -1641,12 +1655,13 @@ unsigned long unmapped_area(struct vm_unmapped_area_info *info)
+ 			}
+ 		}
+ 
+-		gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
++		gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
+ check_current:
+ 		/* Check if current node has a suitable gap */
+ 		if (gap_start > high_limit)
+ 			return -ENOMEM;
+-		if (gap_end >= low_limit && gap_end - gap_start >= length)
++		if (gap_end >= low_limit &&
++		    gap_end > gap_start && gap_end - gap_start >= length)
+ 			goto found;
+ 
+ 		/* Visit right subtree if it looks promising */
+@@ -1668,8 +1683,8 @@ check_current:
+ 			vma = rb_entry(rb_parent(prev),
+ 				       struct vm_area_struct, vm_rb);
+ 			if (prev == vma->vm_rb.rb_left) {
+-				gap_start = vma->vm_prev->vm_end;
+-				gap_end = vma->vm_start;
++				gap_start = vm_end_gap(vma->vm_prev);
++				gap_end = vm_start_gap(vma);
+ 				goto check_current;
+ 			}
+ 		}
+@@ -1733,7 +1748,7 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
+ 
+ 	while (true) {
+ 		/* Visit right subtree if it looks promising */
+-		gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0;
++		gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
+ 		if (gap_start <= high_limit && vma->vm_rb.rb_right) {
+ 			struct vm_area_struct *right =
+ 				rb_entry(vma->vm_rb.rb_right,
+@@ -1746,10 +1761,11 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
+ 
+ check_current:
+ 		/* Check if current node has a suitable gap */
+-		gap_end = vma->vm_start;
++		gap_end = vm_start_gap(vma);
+ 		if (gap_end < low_limit)
+ 			return -ENOMEM;
+-		if (gap_start <= high_limit && gap_end - gap_start >= length)
++		if (gap_start <= high_limit &&
++		    gap_end > gap_start && gap_end - gap_start >= length)
+ 			goto found;
+ 
+ 		/* Visit left subtree if it looks promising */
+@@ -1772,7 +1788,7 @@ check_current:
+ 				       struct vm_area_struct, vm_rb);
+ 			if (prev == vma->vm_rb.rb_right) {
+ 				gap_start = vma->vm_prev ?
+-					vma->vm_prev->vm_end : 0;
++					vm_end_gap(vma->vm_prev) : 0;
+ 				goto check_current;
+ 			}
+ 		}
+@@ -1810,7 +1826,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 		unsigned long len, unsigned long pgoff, unsigned long flags)
+ {
+ 	struct mm_struct *mm = current->mm;
+-	struct vm_area_struct *vma;
++	struct vm_area_struct *vma, *prev;
+ 	struct vm_unmapped_area_info info;
+ 
+ 	if (len > TASK_SIZE - mmap_min_addr)
+@@ -1821,9 +1837,10 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 
+ 	if (addr) {
+ 		addr = PAGE_ALIGN(addr);
+-		vma = find_vma(mm, addr);
++		vma = find_vma_prev(mm, addr, &prev);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-		    (!vma || addr + len <= vma->vm_start))
++		    (!vma || addr + len <= vm_start_gap(vma)) &&
++		    (!prev || addr >= vm_end_gap(prev)))
+ 			return addr;
+ 	}
+ 
+@@ -1846,7 +1863,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 			  const unsigned long len, const unsigned long pgoff,
+ 			  const unsigned long flags)
+ {
+-	struct vm_area_struct *vma;
++	struct vm_area_struct *vma, *prev;
+ 	struct mm_struct *mm = current->mm;
+ 	unsigned long addr = addr0;
+ 	struct vm_unmapped_area_info info;
+@@ -1861,9 +1878,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 	/* requesting a specific address */
+ 	if (addr) {
+ 		addr = PAGE_ALIGN(addr);
+-		vma = find_vma(mm, addr);
++		vma = find_vma_prev(mm, addr, &prev);
+ 		if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
+-				(!vma || addr + len <= vma->vm_start))
++				(!vma || addr + len <= vm_start_gap(vma)) &&
++				(!prev || addr >= vm_end_gap(prev)))
+ 			return addr;
+ 	}
+ 
+@@ -1998,21 +2016,19 @@ find_vma_prev(struct mm_struct *mm, unsigned long addr,
+  * update accounting. This is shared with both the
+  * grow-up and grow-down cases.
+  */
+-static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow)
++static int acct_stack_growth(struct vm_area_struct *vma,
++			     unsigned long size, unsigned long grow)
+ {
+ 	struct mm_struct *mm = vma->vm_mm;
+ 	struct rlimit *rlim = current->signal->rlim;
+-	unsigned long new_start, actual_size;
++	unsigned long new_start;
+ 
+ 	/* address space limit tests */
+ 	if (!may_expand_vm(mm, vma->vm_flags, grow))
+ 		return -ENOMEM;
+ 
+ 	/* Stack limit test */
+-	actual_size = size;
+-	if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN)))
+-		actual_size -= PAGE_SIZE;
+-	if (actual_size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur))
++	if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur))
+ 		return -ENOMEM;
+ 
+ 	/* mlock limit tests */
+@@ -2050,16 +2066,32 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
+ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+ {
+ 	struct mm_struct *mm = vma->vm_mm;
++	struct vm_area_struct *next;
++	unsigned long gap_addr;
+ 	int error = 0;
+ 
+ 	if (!(vma->vm_flags & VM_GROWSUP))
+ 		return -EFAULT;
+ 
+-	/* Guard against wrapping around to address 0. */
+-	if (address < PAGE_ALIGN(address+4))
+-		address = PAGE_ALIGN(address+4);
+-	else
++	/* Guard against exceeding limits of the address space. */
++	address &= PAGE_MASK;
++	if (address >= TASK_SIZE)
+ 		return -ENOMEM;
++	address += PAGE_SIZE;
++
++	/* Enforce stack_guard_gap */
++	gap_addr = address + stack_guard_gap;
++
++	/* Guard against overflow */
++	if (gap_addr < address || gap_addr > TASK_SIZE)
++		gap_addr = TASK_SIZE;
++
++	next = vma->vm_next;
++	if (next && next->vm_start < gap_addr) {
++		if (!(next->vm_flags & VM_GROWSUP))
++			return -ENOMEM;
++		/* Check that both stack segments have the same anon_vma? */
++	}
+ 
+ 	/* We must make sure the anon_vma is allocated. */
+ 	if (unlikely(anon_vma_prepare(vma)))
+@@ -2104,7 +2136,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+ 				if (vma->vm_next)
+ 					vma_gap_update(vma->vm_next);
+ 				else
+-					mm->highest_vm_end = address;
++					mm->highest_vm_end = vm_end_gap(vma);
+ 				spin_unlock(&mm->page_table_lock);
+ 
+ 				perf_event_mmap(vma);
+@@ -2125,6 +2157,8 @@ int expand_downwards(struct vm_area_struct *vma,
+ 				   unsigned long address)
+ {
+ 	struct mm_struct *mm = vma->vm_mm;
++	struct vm_area_struct *prev;
++	unsigned long gap_addr;
+ 	int error;
+ 
+ 	address &= PAGE_MASK;
+@@ -2132,6 +2166,17 @@ int expand_downwards(struct vm_area_struct *vma,
+ 	if (error)
+ 		return error;
+ 
++	/* Enforce stack_guard_gap */
++	gap_addr = address - stack_guard_gap;
++	if (gap_addr > address)
++		return -ENOMEM;
++	prev = vma->vm_prev;
++	if (prev && prev->vm_end > gap_addr) {
++		if (!(prev->vm_flags & VM_GROWSDOWN))
++			return -ENOMEM;
++		/* Check that both stack segments have the same anon_vma? */
++	}
++
+ 	/* We must make sure the anon_vma is allocated. */
+ 	if (unlikely(anon_vma_prepare(vma)))
+ 		return -ENOMEM;
+@@ -2186,28 +2231,25 @@ int expand_downwards(struct vm_area_struct *vma,
+ 	return error;
+ }
+ 
+-/*
+- * Note how expand_stack() refuses to expand the stack all the way to
+- * abut the next virtual mapping, *unless* that mapping itself is also
+- * a stack mapping. We want to leave room for a guard page, after all
+- * (the guard page itself is not added here, that is done by the
+- * actual page faulting logic)
+- *
+- * This matches the behavior of the guard page logic (see mm/memory.c:
+- * check_stack_guard_page()), which only allows the guard page to be
+- * removed under these circumstances.
+- */
++/* enforced gap between the expanding stack and other mappings. */
++unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
++
++static int __init cmdline_parse_stack_guard_gap(char *p)
++{
++	unsigned long val;
++	char *endptr;
++
++	val = simple_strtoul(p, &endptr, 10);
++	if (!*endptr)
++		stack_guard_gap = val << PAGE_SHIFT;
++
++	return 0;
++}
++__setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
++
+ #ifdef CONFIG_STACK_GROWSUP
+ int expand_stack(struct vm_area_struct *vma, unsigned long address)
+ {
+-	struct vm_area_struct *next;
+-
+-	address &= PAGE_MASK;
+-	next = vma->vm_next;
+-	if (next && next->vm_start == address + PAGE_SIZE) {
+-		if (!(next->vm_flags & VM_GROWSUP))
+-			return -ENOMEM;
+-	}
+ 	return expand_upwards(vma, address);
+ }
+ 
+@@ -2229,14 +2271,6 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
+ #else
+ int expand_stack(struct vm_area_struct *vma, unsigned long address)
+ {
+-	struct vm_area_struct *prev;
+-
+-	address &= PAGE_MASK;
+-	prev = vma->vm_prev;
+-	if (prev && prev->vm_end == address) {
+-		if (!(prev->vm_flags & VM_GROWSDOWN))
+-			return -ENOMEM;
+-	}
+ 	return expand_downwards(vma, address);
+ }
+ 
+@@ -2334,7 +2368,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
+ 		vma->vm_prev = prev;
+ 		vma_gap_update(vma);
+ 	} else
+-		mm->highest_vm_end = prev ? prev->vm_end : 0;
++		mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
+ 	tail_vma->vm_next = NULL;
+ 
+ 	/* Kill the cache */
+-- 
+2.12.3
+