Commits
Tetsuo Handa committed caa6926d94f
/dev/mem: Bail out upon SIGKILL. commit 8619e5bdeee8b2c685d686281f2d2a6017c4bc15 upstream. syzbot found that a thread can stall for minutes inside read_mem() or write_mem() after that thread was killed by SIGKILL [1]. Reading from iomem areas of /dev/mem can be slow, depending on the hardware. While reading 2GB at one read() is legal, delaying termination of killed thread for minutes is bad. Thus, allow reading/writing /dev/mem and /dev/kmem to be preemptible and killable. [ 1335.912419][T20577] read_mem: sz=4096 count=2134565632 [ 1335.943194][T20577] read_mem: sz=4096 count=2134561536 [ 1335.978280][T20577] read_mem: sz=4096 count=2134557440 [ 1336.011147][T20577] read_mem: sz=4096 count=2134553344 [ 1336.041897][T20577] read_mem: sz=4096 count=2134549248 Theoretically, reading/writing /dev/mem and /dev/kmem can become "interruptible". But this patch chose "killable". Future patch will make them "interruptible" so that we can revert to "killable" if some program regressed. [1] https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Cc: stable <stable@vger.kernel.org> Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com> Link: https://lore.kernel.org/r/1566825205-10703-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>