3.2.56-rc1 review patch. If anyone has any objections, please let me know. ------------------ 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> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- mm/swapfile.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -1649,7 +1649,6 @@ SYSCALL_DEFINE1(swapoff, const char __us p->max = 0; swap_map = p->swap_map; p->swap_map = NULL; - p->flags = 0; spin_unlock(&swap_lock); mutex_unlock(&swapon_mutex); vfree(swap_map); @@ -1667,6 +1666,16 @@ 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); -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html