> On May 5, 2020, at 2:57 PM, Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: > > On Mon, May 04, 2020 at 03:11:09PM -0400, Qian Cai wrote: >> Running a syscall fuzzer inside a container on linux-next floods systems with soft lockups. It looks like stuck in this line at iov_iter_copy_from_user_atomic(), Thoughts? >> >> iterate_all_kinds(i, bytes, v, >> copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len), >> memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page, >> v.bv_offset, v.bv_len), >> memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len) >> ) > > If the size being copied is large enough, something like this might happen. > > Is this a CONFIG_PREEMPT=n kernel? And is the size passed in to Yes, CONFIG_PREEMPT=n. > iov_iter_copy_from_user_atomic() quite large, given that this is generated > by a fuzzer? If so, one thing to try is to add cond_resched() in the > iterate_bvec(), iterate_kvec(), and iterate_iovec() macros. I’ll try that.
