On Mon, Sep 29, 2014 at 09:27:09PM -0700, Linus Torvalds wrote: > On Mon, Sep 29, 2014 at 8:33 PM, Dave Jones <da...@redhat.com> wrote: > > > > Looking at the dump, there's only one running trinity child, > > with all the others blocking on it. > > > > trinity-c49 R running task 12856 19464 7633 0x00000004 > > ffff8800a09bf960 0000000000000002 ffff8800a09bf9f8 ffff880219650000 > > 00000000001d4080 0000000000000000 ffff8800a09bffd8 00000000001d4080 > > ffff88023f755bc0 ffff880219650000 ffff8800a09bffd8 ffff88010b017e00 > > Call Trace: > > [<ffffffff911c3c67>] handle_mm_fault+0x3a7/0xcd0 > > [<ffffffff91042c84>] __do_page_fault+0x1a4/0x600 > > [<ffffffff910430fe>] do_page_fault+0x1e/0x70 > > [<ffffffff918264b2>] page_fault+0x22/0x30 > > [<ffffffff911bd7e3>] ? copy_page_to_iter+0x3b3/0x500 > > [<ffffffff9120eddf>] pipe_read+0xdf/0x330 > > > > Running the function tracer on that pid shows it spinning forever.. > > http://codemonkey.org.uk/junk/pipe-trace.txt > > > > Kernel bug (missing EFAULT check somewhere perhaps?), or is this a > > case where the fuzzer asked the kernel to do something stupid, and it > > obliged ? > > Hmm. It looks like copy_page_to_iter_iovec() is broken and keeps not > making any progress while just faulting. > > I don't see how that could happen, though. All the loops there are > conditional on the user copies *not* failing (ie "!left"), and they > seem to properly update "iov". > > Mind sending a disassembly of your "copy_page_to_iter" function, in > particular around that whole "0x3b3/0x500" area which is where the > page fault seems to happen? > > Adding Al to the cc, since this code is from his commit 6e58e79db8a1 > ("introduce copy_page_to_iter, kill loop over iovec in > generic_file_aio_read()") but I don't see anything obviously wrong > there. > > Al? Do you see something I don't? Dave's function trace does seem to > say that it doesn't even get back to pipe_read(), though, so the loop > really must be inside copy_page_to_iter().
I'll take a look tomorrow morning after I get some sleep - 19 hours of uptime, on top of 5 hours of sleep, on top of ~20 hours of uptime ;-/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
