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authorLinus Torvalds <torvalds@linux-foundation.org>2010-08-14 11:44:56 -0700
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-20 11:55:38 -0700
commit16af977da0867b1f9fdc98fb61f10ef85a7b60e7 (patch)
tree6ae385b5479335351737ee7e11113e87ab53c80e
parentf6b0f3c69141a21f12cb2f678b0cdaa2be8076a7 (diff)
downloadlinux-2.6.34-ux500-16af977da0867b1f9fdc98fb61f10ef85a7b60e7.tar.gz
mm: fix page table unmap for stack guard page properly
commit 11ac552477e32835cb6970bf0a70c210807f5673 upstream. We do in fact need to unmap the page table _before_ doing the whole stack guard page logic, because if it is needed (mainly 32-bit x86 with PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it will do a kmap_atomic/kunmap_atomic. And those kmaps will create an atomic region that we cannot do allocations in. However, the whole stack expand code will need to do anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an atomic region. Now, a better model might actually be to do the anon_vma_prepare() when _creating_ a VM_GROWSDOWN segment, and not have to worry about any of this at page fault time. But in the meantime, this is the straightforward fix for the issue. See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details. Reported-by: Wylda <wylda@volny.cz> Reported-by: Sedat Dilek <sedat.dilek@gmail.com> Reported-by: Mike Pagano <mpagano@gentoo.org> Reported-by: Fran├žois Valenduc <francois.valenduc@tvcablenet.be> Tested-by: Ed Tomlinson <edt@aei.ca> Cc: Pekka Enberg <penberg@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--mm/memory.c13
1 files changed, 6 insertions, 7 deletions
diff --git a/mm/memory.c b/mm/memory.c
index aaaedbd2080..307bf77fc44 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2792,24 +2792,23 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
spinlock_t *ptl;
pte_t entry;
- if (check_stack_guard_page(vma, address) < 0) {
- pte_unmap(page_table);
+ pte_unmap(page_table);
+
+ /* Check if we need to add a guard page to the stack */
+ if (check_stack_guard_page(vma, address) < 0)
return VM_FAULT_SIGBUS;
- }
+ /* Use the zero-page for reads */
if (!(flags & FAULT_FLAG_WRITE)) {
entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
vma->vm_page_prot));
- ptl = pte_lockptr(mm, pmd);
- spin_lock(ptl);
+ page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
if (!pte_none(*page_table))
goto unlock;
goto setpte;
}
/* Allocate our own private page. */
- pte_unmap(page_table);
-
if (unlikely(anon_vma_prepare(vma)))
goto oom;
page = alloc_zeroed_user_highpage_movable(vma, address);