On 2022/4/25 15:45, David Hildenbrand wrote: > On 25.04.22 03:08, HORIGUCHI NAOYA(堀口 直也) wrote: >> On Sun, Apr 24, 2022 at 05:11:03PM +0800, Miaohe Lin wrote: >>> There is a bug in unuse_pte(): when swap page happens to be unreadable, >>> page filled with random data is mapped into user address space. In case >>> of error, a special swap entry indicating swap read fails is set to the >>> page table. So the swapcache page can be freed and the user won't end up >>> with a permanently mounted swap because a sector is bad. And if the page >>> is accessed later, the user process will be killed so that corrupted data >>> is never consumed. On the other hand, if the page is never accessed, the >>> user won't even notice it. >>> >>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> >>> Acked-by: David Hildenbrand <david@xxxxxxxxxx> >> >> Hi Miaohe, >> >> This bug sounds relatively serious to me, and it seems old, so is it worth >> sending to -stable? > > I'm not sure if this is worth -stable, but no strong opinion. I have no strong opinion too. I'm just afraid someone might run into it. But swapoff is expected to be a rare operation anyway... > > The do_swap_page() part was added in 2005: > > commit b81074800b98ac50b64d4c8d34e8abf0fda5e3d1 > Author: Kirill Korotaev <dev@xxxxx> > Date: Mon May 16 21:53:50 2005 -0700 > > [PATCH] do_swap_page() can map random data if swap read fails > > There is a bug in do_swap_page(): when swap page happens to be unreadable, > page filled with random data is mapped into user address space. The fix is > to check for PageUptodate and send SIGBUS in case of error. > > Signed-Off-By: Kirill Korotaev <dev@xxxxx> > Signed-Off-By: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx> > Acked-by: Hugh Dickins <hugh@xxxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxx> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxx> > > So the do_swap_page() part has been fixed for quite a while already. Does this mean only do_swap_page maps random data if swap read fails is observed from that time on? So this might not be worth -stable as it's never seen more than a decade? Thanks! >
