73 lines
2.8 KiB
Diff
73 lines
2.8 KiB
Diff
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From 3e4f09eef73ad12d4876e24daf52a0dc0891d7da Mon Sep 17 00:00:00 2001
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From: Michal Hocko <mhocko@suse.com>
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Date: Mon, 17 Jul 2017 14:53:28 +0200
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Subject: [PATCH 1/2] mm/mmap.c: do not blow on PROT_NONE MAP_FIXED holes in
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the stack
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Commit 1be7107fbe18 ("mm: larger stack guard gap, between vmas") has
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introduced a regression in some rust and Java environments which are
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trying to implement their own stack guard page. They are punching a new
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MAP_FIXED mapping inside the existing stack Vma.
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This will confuse expand_{downwards,upwards} into thinking that the
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stack expansion would in fact get us too close to an existing non-stack
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vma which is a correct behavior wrt safety. It is a real regression on
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the other hand.
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Let's work around the problem by considering PROT_NONE mapping as a part
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of the stack. This is a gros hack but overflowing to such a mapping
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would trap anyway an we only can hope that usespace knows what it is
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doing and handle it propely.
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Fixes: 1be7107fbe18 ("mm: larger stack guard gap, between vmas")
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Link: http://lkml.kernel.org/r/20170705182849.GA18027@dhcp22.suse.cz
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Signed-off-by: Michal Hocko <mhocko@suse.com>
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Debugged-by: Vlastimil Babka <vbabka@suse.cz>
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Cc: Ben Hutchings <ben@decadent.org.uk>
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Cc: Willy Tarreau <w@1wt.eu>
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Cc: Oleg Nesterov <oleg@redhat.com>
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Cc: Rik van Riel <riel@redhat.com>
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Cc: Hugh Dickins <hughd@google.com>
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Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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CVE-2017-1000364
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(cherry picked from commit 561b5e0709e4a248c67d024d4d94b6e31e3edf2f)
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Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
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Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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Acked-by: Kamal Mostafa <kamal@canonical.com>
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Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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mm/mmap.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/mm/mmap.c b/mm/mmap.c
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index ef78a5ca5599..9fabd8c82f38 100644
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--- a/mm/mmap.c
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+++ b/mm/mmap.c
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@@ -2240,7 +2240,8 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
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gap_addr = TASK_SIZE;
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next = vma->vm_next;
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- if (next && next->vm_start < gap_addr) {
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+ if (next && next->vm_start < gap_addr &&
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+ (next->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
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if (!(next->vm_flags & VM_GROWSUP))
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return -ENOMEM;
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/* Check that both stack segments have the same anon_vma? */
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@@ -2324,7 +2325,8 @@ int expand_downwards(struct vm_area_struct *vma,
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if (gap_addr > address)
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return -ENOMEM;
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prev = vma->vm_prev;
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- if (prev && prev->vm_end > gap_addr) {
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+ if (prev && prev->vm_end > gap_addr &&
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+ (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
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if (!(prev->vm_flags & VM_GROWSDOWN))
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return -ENOMEM;
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/* Check that both stack segments have the same anon_vma? */
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--
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2.11.0
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