On 2022/4/26 8:31, HORIGUCHI NAOYA(堀口 直也) wrote: > On Mon, Apr 25, 2022 at 04:47:41PM +0800, Miaohe Lin wrote: >> 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? > > OK, both choices seems possible, so not sending to -stable is fine to me. > It's finally up to you. I tend not to send it to -stable due to the above concern now. Thanks! > > Thanks, > Naoya Horiguchi >
