On Wed, Jun 12, 2019 at 09:29:48AM +0200, Thomas Gleixner wrote: > On Wed, 12 Jun 2019, Greg KH wrote: > > On Wed, Jun 12, 2019 at 09:50:25AM +0800, zhangxiaoxu (A) wrote: > > > This patch is for stable branch linux-4.4-y. > > > > > > On 2019/6/12 9:54, ZhangXiaoxu wrote: > > > > The upstram commit 65d8fc777f6d ("futex: Remove requirement > > > > for lock_page() in get_futex_key()") use variable 'page' as > > > > the page head, when merge it to stable branch, the variable > > > > `page_head` is page head. > > > > > > > > In the stable branch, the variable `page` not means the page > > > > head, when lock the page head, we should lock 'page_head', > > > > rather than 'page'. > > > > > > > > It maybe lead a hung task problem. > > > > > > > > Signed-off-by: ZhangXiaoxu <zhangxiaoxu5@xxxxxxxxxx> > > > > Cc: stable@xxxxxxxxxxxxxxx > > > > --- > > > > kernel/futex.c | 4 ++-- > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > I do not understand. > > > > Please read > > https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html > > for how to submit a patch to the stable trees properly. > > > > If the commit is not in Linus's tree, then we can not take it, unless > > something is _very_ broken and it is the only way it can be resolved. > > There is something _very_ broken. Upstream is correct but the 4.4. backport > of the above commit is broken (93dcb09e29bb24a86aa7b7eff65e424f7dc98af2) in > the way Zhang described. So it's a 4.4. only issue. That wasn't obvious at all, and wasn't cc:ed to stable to start with... Anyway, I'll go queue this up to the 4.4.y tree if no one objects... thanks, greg k-h