On Wed, Aug 21, 2019 at 07:06:51AM +0900, Tetsuo Handa wrote: > syzbot found that a thread can stall for minutes inside read_mem() > after that thread was killed by SIGKILL [1]. Reading 2GB at one read() > is legal, but delaying termination of killed thread for minutes is bad. > > [ 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 > > [1] > https://syzkaller.appspot.com/bug?id=a0e3436829698d5824231251fad9d8e998f94f5e > > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6c...@syzkaller.appspotmail.com> > --- > drivers/char/mem.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/char/mem.c b/drivers/char/mem.c > index b08dc50..0f7d4c4 100644 > --- a/drivers/char/mem.c > +++ b/drivers/char/mem.c > @@ -135,7 +135,7 @@ static ssize_t read_mem(struct file *file, char __user > *buf, > if (!bounce) > return -ENOMEM; > > - while (count > 0) { > + while (count > 0 && !fatal_signal_pending(current)) { > unsigned long remaining; > int allowed, probe; > > -- > 1.8.3.1 >
Oh, nice! This shouldn't break anything that is assuming that the read will complete before a signal is delivered, right? I know userspace handling of "short" reads is almost always not there... thanks, greg k-h
