From: Miaohe Lin linmiaohe@huawei.com
[ Upstream commit 2efa33fc7f6ec94a3a538c1a264273c889be2b36 ]
When I was investigating the swap code, I found the below possible race window:
CPU 1 CPU 2 ----- ----- shmem_swapin swap_cluster_readahead if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) { swapoff .. si->swap_file = NULL; .. struct inode *inode = si->swap_file->f_mapping->host;[oops!]
Close this race window by using get/put_swap_device() to guard against concurrent swapoff.
Link: https://lkml.kernel.org/r/20210426123316.806267-5-linmiaohe@huawei.com Fixes: 8fd2e0b505d1 ("mm: swap: check if swap backing device is congested or not") Signed-off-by: Miaohe Lin linmiaohe@huawei.com Reviewed-by: "Huang, Ying" ying.huang@intel.com Cc: Dennis Zhou dennis@kernel.org Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Hugh Dickins hughd@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@suse.com Cc: Joonsoo Kim iamjoonsoo.kim@lge.com Cc: Alex Shi alexs@kernel.org Cc: Matthew Wilcox willy@infradead.org Cc: Minchan Kim minchan@kernel.org Cc: Wei Yang richard.weiyang@gmail.com Cc: Yang Shi shy828301@gmail.com Cc: David Hildenbrand david@redhat.com Cc: Yu Zhao yuzhao@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- mm/shmem.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c index 6e487bf555f9..a847cba3c226 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1698,7 +1698,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, struct address_space *mapping = inode->i_mapping; struct shmem_inode_info *info = SHMEM_I(inode); struct mm_struct *charge_mm = vma ? vma->vm_mm : current->mm; - struct page *page; + struct swap_info_struct *si; + struct page *page = NULL; swp_entry_t swap; int error;
@@ -1706,6 +1707,12 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, swap = radix_to_swp_entry(*pagep); *pagep = NULL;
+ /* Prevent swapoff from happening to us. */ + si = get_swap_device(swap); + if (!si) { + error = EINVAL; + goto failed; + } /* Look it up and read it in.. */ page = lookup_swap_cache(swap, NULL, 0); if (!page) { @@ -1767,6 +1774,8 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, swap_free(swap);
*pagep = page; + if (si) + put_swap_device(si); return 0; failed: if (!shmem_confirm_swap(mapping, index, swap)) @@ -1777,6 +1786,9 @@ unlock: put_page(page); }
+ if (si) + put_swap_device(si); + return error; }