diff options
| author | Weijie Yang <weijie.yang@samsung.com> | 2014-02-06 12:04:23 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-02-20 11:08:00 -0800 |
| commit | 6fe9f7abe5f08c141fac3242894504b066da9b8d (patch) | |
| tree | 581d13a769df00733fbf28ca699ff3e50b9102b5 /mm | |
| parent | 78db0017d8f53578f88102f2f303ef57a139f0ba (diff) | |
mm/swap: fix race on swap_info reuse between swapoff and swapon
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@linux-foundation.org: tidy up code comment]
Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/swapfile.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c index de7c904e52e..0ec2eaf3ccf 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1922,7 +1922,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile) 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 __user *, specialfile) 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); |