On 2021/4/13 9:36, Huang, Ying wrote: > Miaohe Lin <linmiaohe@xxxxxxxxxx> writes: > >> swap_cluster_readahead() could race with swapoff and might dereference >> si->swap_file after it's released by swapoff. Close this race window by >> using get/put_swap_device() pair. > > I think we should fix the callers instead to reduce the overhead. Now, > do_swap_page() has been fixed. We need to fix shmem_swapin(). > Will do. Many thanks. > Best Regards, > Huang, Ying > >> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> >> --- >> mm/swap_state.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/mm/swap_state.c b/mm/swap_state.c >> index 3bf0d0c297bc..eba6b0cf6cf9 100644 >> --- a/mm/swap_state.c >> +++ b/mm/swap_state.c >> @@ -626,12 +626,17 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, >> unsigned long offset = entry_offset; >> unsigned long start_offset, end_offset; >> unsigned long mask; >> - struct swap_info_struct *si = swp_swap_info(entry); >> + struct swap_info_struct *si; >> struct blk_plug plug; >> bool do_poll = true, page_allocated; >> struct vm_area_struct *vma = vmf->vma; >> unsigned long addr = vmf->address; >> >> + si = get_swap_device(entry); >> + /* In case we raced with swapoff. */ >> + if (!si) >> + return NULL; >> + >> mask = swapin_nr_pages(offset) - 1; >> if (!mask) >> goto skip; >> @@ -673,7 +678,9 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask, >> >> lru_add_drain(); /* Push any new pages onto the LRU now */ >> skip: >> - return read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll); >> + page = read_swap_cache_async(entry, gfp_mask, vma, addr, do_poll); >> + put_swap_device(si); >> + return page; >> } >> >> int init_swap_address_space(unsigned int type, unsigned long nr_pages) > . >
