Subject: + mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch added to -mm tree To: weijie.yang@xxxxxxxxxxx,hughd@xxxxxxxxxx From: akpm@xxxxxxxxxxxxxxxxxxxx Date: Fri, 10 Jan 2014 16:38:34 -0800 The patch titled Subject: mm/swap: fix race on swap_info reuse between swapoff and swapon has been added to the -mm tree. Its filename is mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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. Signed-off-by: Weijie Yang <weijie.yang@xxxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> 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 @@ -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); spin_unlock(&p->lock); spin_unlock(&swap_lock); @@ -1948,6 +1947,16 @@ SYSCALL_DEFINE1(swapoff, const char __us mutex_unlock(&inode->i_mutex); } filp_close(swap_file, NULL); + + /* + * clear SWP_USED flag after all resources 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 mm-zswapc-change-params-from-hidden-to-ro.patch mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html