Subject: [merged] mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch removed from -mm tree
To: weijie.yang@xxxxxxxxxxx,hughd@xxxxxxxxxx,k.kozlowski@xxxxxxxxxxx,stable@xxxxxxxxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 07 Feb 2014 12:18:41 -0800
The patch titled
Subject: mm/swap: fix race on swap_info reuse between swapoff and swapon
has been removed from the -mm tree. Its filename was
mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Weijie Yang <weijie.yang@xxxxxxxxxxx>
Subject: mm/swap: fix race on swap_info reuse between swapoff and swapon
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>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/swapfile.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff -puN mm/swapfile.c~mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon mm/swapfile.c
--- a/mm/swapfile.c~mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon
+++ a/mm/swapfile.c
@@ -1923,7 +1923,6 @@ 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);
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
@@ -1949,6 +1948,16 @@ 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 -mm which might be from weijie.yang@xxxxxxxxxxx are
origin.patch
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