On 07/09/2018 01:50 PM, Dmitry Vyukov wrote: > On Mon, Jul 9, 2018 at 10:34 PM, syzbot > <syzbot+e9f364d3b15ce41d8451@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >> Hello, >> >> syzbot found the following crash on: >> >> HEAD commit: 1e4b044d2251 Linux 4.18-rc4 >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=1414c2c2400000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=25856fac4e580aa7 >> dashboard link: https://syzkaller.appspot.com/bug?extid=e9f364d3b15ce41d8451 >> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >> >> Unfortunately, I don't have any reproducer for this crash yet. >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+e9f364d3b15ce41d8451@xxxxxxxxxxxxxxxxxxxxxxxxx > > Looks like the problem is actually in nfc, so +nfc maintainers. Note this issue was discussed before, maybe we should patch NFC without waiting for nfc maintainer. ---------------------------------------------------- On 06/25/2018 10:12 PM, Sergey Senozhatsky wrote: > On (06/26/18 07:07), Dmitry Vyukov wrote: > [..] >>> #include <net/nfc/nfc.h> >>> @@ -755,7 +756,8 @@ int nfc_llcp_send_ui_frame(struct nfc_llcp_sock *sock, u8 ssap, u8 dsap, >>> pdu = nfc_alloc_send_skb(sock->dev, &sock->sk, MSG_DONTWAIT, >>> frag_len + LLCP_HEADER_SIZE, &err); >>> if (pdu == NULL) { >>> - pr_err("Could not allocate PDU\n"); >>> + pr_err_ratelimited("Could not allocate PDU\n"); >>> + cond_resched(); >>> continue; >>> } >> >> >> But this thread is still in an infinite (unkillable?) loop? If yes, we >> are waiting for the next syzbot report > > The loop is still infinite, correct, but we have a preemption point now. > Sure, net people can come with a much better solution, I'll be happy to > scratch my patch. > This can not be the right solution, think about current thread being real time, cond_resched() might be a nop. We should probably not loop at all, or not use MSG_DONTWAIT. (And remove this useless "Could not allocate PDU" message) NFC maintainers should really take a look at this.
