| Message ID | 20210408130820.48233-6-linmiaohe@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | close various race windows for swap | expand |
Miaohe Lin <linmiaohe@huawei.com> 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(). Best Regards, Huang, Ying > Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> > --- > 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)
On 2021/4/13 9:36, Huang, Ying wrote: > Miaohe Lin <linmiaohe@huawei.com> 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@huawei.com> >> --- >> 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) > . >
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)
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. Signed-off-by: Miaohe Lin <linmiaohe@huawei.com> --- mm/swap_state.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)