Messages in this thread | | | Subject | Re: [PATCH v3] /dev/mem: Bail out upon SIGKILL. | From | Tetsuo Handa <> | Date | Wed, 4 Sep 2019 19:19:47 +0900 |
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Ping? Syzbot is still reporting this problem.
On 2019/08/26 22:44, Tetsuo Handa wrote: > On 2019/08/26 22:29, Greg Kroah-Hartman wrote: >> On Mon, Aug 26, 2019 at 10:13:25PM +0900, Tetsuo Handa wrote: >>> 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> >>> Reported-by: syzbot <syzbot+8ab2d0f39fb79fe6ca40@syzkaller.appspotmail.com> >>> --- >>> drivers/char/mem.c | 21 +++++++++++++++++++++ >>> 1 file changed, 21 insertions(+) >> >> What changed from previous versions? >> >> That goes below the --- line at the very least. > > (1) Moved fatal_signal_pending() test to end of iteration. > (2) Added need_resched() test before cond_resched(). > (3) Removed -EINTR assignment because end of iteration means > that at least one byte was processed (sz > 0). > >> >> thanks, >> >> greg k-h >> >
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