This is a note to let you know that I've just added the patch titled
mm/swap: fix race on swap_info reuse between swapoff and swapon
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f893ab41e4dae2fe8991faf5d86d029068d1ef3a Mon Sep 17 00:00:00 2001
From: Weijie Yang <weijie.yang@xxxxxxxxxxx>
Date: Thu, 6 Feb 2014 12:04:23 -0800
Subject: mm/swap: fix race on swap_info reuse between swapoff and swapon
From: Weijie Yang <weijie.yang@xxxxxxxxxxx>
commit f893ab41e4dae2fe8991faf5d86d029068d1ef3a upstream.
swapoff clear swap_info's SWP_USED flag prematurely and free its
resources after that. A concurrent swapon will reuse this swap_info
while its previous resources are not cleared completely.
These late freed resources are:
- p->percpu_cluster
- swap_cgroup_ctrl[type]
- block_device setting
- inode->i_flags &= ~S_SWAPFILE
This patch clears the SWP_USED flag after all its resources are freed,
so that swapon can reuse this swap_info by alloc_swap_info() safely.
[akpm@xxxxxxxxxxxxxxxxxxxx: tidy up code comment]
Signed-off-by: Weijie Yang <weijie.yang@xxxxxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1922,7 +1922,6 @@ SYSCALL_DEFINE1(swapoff, const char __us
p->swap_map = NULL;
cluster_info = p->cluster_info;
p->cluster_info = NULL;
- p->flags = 0;
frontswap_map = frontswap_map_get(p);
frontswap_map_set(p, NULL);
spin_unlock(&p->lock);
@@ -1948,6 +1947,16 @@ SYSCALL_DEFINE1(swapoff, const char __us
mutex_unlock(&inode->i_mutex);
}
filp_close(swap_file, NULL);
+
+ /*
+ * Clear the SWP_USED flag after all resources are freed so that swapon
+ * can reuse this swap_info in alloc_swap_info() safely. It is ok to
+ * not hold p->lock after we cleared its SWP_WRITEOK.
+ */
+ spin_lock(&swap_lock);
+ p->flags = 0;
+ spin_unlock(&swap_lock);
+
err = 0;
atomic_inc(&proc_poll_event);
wake_up_interruptible(&proc_poll_wait);
Patches currently in stable-queue which might be from weijie.yang@xxxxxxxxxxx are
queue-3.12/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch
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