From: Vlastimil Babka <[email protected]>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit 9050d7eba40b3d79551668f54e68fd6f51945ef3 upstream.
Daniel Borkmann reported a VM_BUG_ON assertion failing:
------------[ cut here ]------------
kernel BUG at mm/mlock.c:528!
invalid opcode: 0000 [#1] SMP
Modules linked in: ccm arc4 iwldvm [...]
video
CPU: 3 PID: 2266 Comm: netsniff-ng Not tainted 3.14.0-rc2+ #8
Hardware name: LENOVO 2429BP3/2429BP3, BIOS G4ET37WW (1.12 ) 05/29/2012
task: ffff8801f87f9820 ti: ffff88002cb44000 task.ti: ffff88002cb44000
RIP: 0010:[<ffffffff81171ad0>] [<ffffffff81171ad0>]
munlock_vma_pages_range+0x2e0/0x2f0
Call Trace:
do_munmap+0x18f/0x3b0
vm_munmap+0x41/0x60
SyS_munmap+0x22/0x30
system_call_fastpath+0x1a/0x1f
RIP munlock_vma_pages_range+0x2e0/0x2f0
---[ end trace a0088dcf07ae10f2 ]---
because munlock_vma_pages_range() thinks it's unexpectedly in the middle
of a THP page. This can be reproduced with default config since 3.11
kernels. A reproducer can be found in the kernel's selftest directory
for networking by running ./psock_tpacket.
The problem is that an order=2 compound page (allocated by
alloc_one_pg_vec_page() is part of the munlocked VM_MIXEDMAP vma (mapped
by packet_mmap()) and mistaken for a THP page and assumed to be order=9.
The checks for THP in munlock came with commit ff6a6da60b89 ("mm:
accelerate munlock() treatment of THP pages"), i.e. since 3.9, but did
not trigger a bug. It just makes munlock_vma_pages_range() skip such
compound pages until the next 512-pages-aligned page, when it encounters
a head page. This is however not a problem for vma's where mlocking has
no effect anyway, but it can distort the accounting.
Since commit 7225522bb429 ("mm: munlock: batch non-THP page isolation
and munlock+putback using pagevec") this can trigger a VM_BUG_ON in
PageTransHuge() check.
This patch fixes the issue by adding VM_MIXEDMAP flag to VM_SPECIAL, a
list of flags that make vma's non-mlockable and non-mergeable. The
reasoning is that VM_MIXEDMAP vma's are similar to VM_PFNMAP, which is
already on the VM_SPECIAL list, and both are intended for non-LRU pages
where mlocking makes no sense anyway. Related Lkml discussion can be
found in [2].
[1] tools/testing/selftests/net/psock_tpacket
[2] https://lkml.org/lkml/2014/1/10/427
Signed-off-by: Vlastimil Babka <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Reported-by: Daniel Borkmann <[email protected]>
Tested-by: Daniel Borkmann <[email protected]>
Cc: Thomas Hellstrom <[email protected]>
Cc: John David Anglin <[email protected]>
Cc: HATAYAMA Daisuke <[email protected]>
Cc: Konstantin Khlebnikov <[email protected]>
Cc: Carsten Otte <[email protected]>
Cc: Jared Hulbert <[email protected]>
Tested-by: Hannes Frederic Sowa <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Acked-by: Rik van Riel <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Jiri Slaby <[email protected]>
---
include/linux/mm.h | 2 +-
mm/huge_memory.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index fed08c0c543b..648bcb007eba 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -161,7 +161,7 @@ extern unsigned int kobjsize(const void *objp);
* Special vmas that are non-mergable, non-mlock()able.
* Note: mm/huge_memory.c VM_NO_THP depends on this definition.
*/
-#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP)
+#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)
/*
* mapping from the currently active vm_flags protection bits (the
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index dd7789ce7572..389973fd6bb7 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1897,7 +1897,7 @@ out:
return ret;
}
-#define VM_NO_THP (VM_SPECIAL|VM_MIXEDMAP|VM_HUGETLB|VM_SHARED|VM_MAYSHARE)
+#define VM_NO_THP (VM_SPECIAL | VM_HUGETLB | VM_SHARED | VM_MAYSHARE)
int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
--
1.9.0
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