Re: [PATCH akpm] mm: include VM_MIXEDMAP flag in the VM_SPECIAL list to avoid m(un)locking
From: Vlastimil Babka
Date: Wed Feb 19 2014 - 04:26:55 EST
On 02/16/2014 03:59 PM, Daniel Borkmann wrote:
From: Vlastimil Babka <vbabka@xxxxxxx>
[ 4366.519657] ------------[ cut here ]------------
[ 4366.519709] kernel BUG at mm/mlock.c:528!
[ 4366.519742] invalid opcode: 0000 [#1] SMP
[ 4366.519782] Modules linked in: ccm arc4 iwldvm [...]
[ 4366.520488] video
[ 4366.520501] CPU: 3 PID: 2266 Comm: netsniff-ng Not tainted 3.14.0-rc2+ #8
[ 4366.520551] Hardware name: LENOVO 2429BP3/2429BP3, BIOS G4ET37WW (1.12 ) 05/29/2012
[ 4366.520608] task: ffff8801f87f9820 ti: ffff88002cb44000 task.ti: ffff88002cb44000
[ 4366.520662] RIP: 0010:[<ffffffff81171ad0>] [<ffffffff81171ad0>] munlock_vma_pages_range+0x2e0/0x2f0
[ 4366.520738] RSP: 0018:ffff88002cb45e00 EFLAGS: 00010206
[ 4366.520777] RAX: 00000000000001ff RBX: ffff8801f5e75d10 RCX: 000000000000107d
[ 4366.520829] RDX: 00000007f133345f RSI: ffffea0007d76000 RDI: ffffea0007d76000
[ 4366.520881] RBP: ffff88002cb45ed8 R08: 0000000000000000 R09: a8001f5d80000000
[ 4366.520932] R10: 57ffcaa287d76000 R11: 0000000000000246 R12: ffffea0007d76000
[ 4366.520983] R13: 00007f133745f000 R14: 00007f133345f000 R15: ffff8801f5e75a50
[ 4366.521036] FS: 00007f133745f740(0000) GS:ffff88021e2c0000(0000) knlGS:0000000000000000
[ 4366.521094] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 4366.521137] CR2: 000000000062ead0 CR3: 00000000c688d000 CR4: 00000000001407e0
[ 4366.521188] Stack:
[ 4366.521205] ffffffff8116b085 00007f133745efff 00007f133327d000 00007f133745f000
[ 4366.521269] 000001ff81172793 ffff8800c6baa6e0 0000000000000000 0000000000000000
[ 4366.521333] 00007f1333336000 ffffea0004a7ab40 ffff88002cb45e58 0000000000000000
[ 4366.521397] Call Trace:
[ 4366.521422] [<ffffffff8116b085>] ? tlb_finish_mmu+0x35/0x60
[ 4366.521468] [<ffffffff8117486f>] do_munmap+0x18f/0x3b0
[ 4366.521511] [<ffffffff8163e84b>] ? packet_getsockopt+0xfb/0x310
[ 4366.521558] [<ffffffff81174ad1>] vm_munmap+0x41/0x60
[ 4366.521598] [<ffffffff811759b2>] SyS_munmap+0x22/0x30
[ 4366.521639] [<ffffffff81666616>] system_call_fastpath+0x1a/0x1f
[ 4366.521683] Code: ff ff e8 c4 07 fe ff 84 c0 48 8b 95 28 ff ff ff 0f 85 52 ff ff
ff e9 3e ff ff ff 48 89 d7 e8 bf 32 4e 00 4c 89 e7 e8 aa 32 4e
00 <0f> 0b 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44
00 00
[ 4366.522004] RIP [<ffffffff81171ad0>] munlock_vma_pages_range+0x2e0/0x2f0
[ 4366.522059] RSP <ffff88002cb45e00>
[ 4366.539269] ---[ end trace a0088dcf07ae10f2 ]---
Daniel Borkmann reported a bug (stack trace above) with VM_BUG_ON
assertions failing where 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 7225522bb ("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 <vbabka@xxxxxxx>
Reported-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Tested-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Cc: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Cc: John David Anglin <dave.anglin@xxxxxxxx>
Cc: HATAYAMA Daisuke <d.hatayama@xxxxxxxxxxxxxx>
Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
Cc: Carsten Otte <cotte@xxxxxxxxxx>
Cc: Jared Hulbert <jaredeh@xxxxxxxxx>
Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.11.x+]
---
Took the liberty to resubmit it, as people hit that on distribution
kernels; tested and it looks to fix the issue.
Thanks for resubmitting and improving the changelog. I've been away last
week.
Vlastimil
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 f28f46e..f9b04ac 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -175,7 +175,7 @@ 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 82166bf..1387969 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1963,7 +1963,7 @@ 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)
--
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