Messages in this thread | | | Date | Sat, 23 Jan 2016 21:05:11 +0100 | From | Daniel Borkmann <> | Subject | Re: net: GPF in netlink_getsockbyportid |
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On 01/23/2016 08:25 PM, Florian Westphal wrote: > Dmitry Vyukov <dvyukov@google.com> wrote: > > [ CC nf-devel, not sure if its nfnetlink fault or NETLINK_MMAP ] > >> The following program causes GPF in netlink_getsockbyportid: >> >> // autogenerated by syzkaller (http://github.com/google/syzkaller) >> #include <pthread.h> >> #include <stdint.h> >> #include <string.h> >> #include <sys/syscall.h> >> #include <unistd.h> >> >> int main() >> { >> syscall(SYS_mmap, 0x20000000ul, 0xe65000ul, 0x3ul, 0x32ul, >> 0xfffffffffffffffful, 0x0ul); >> int fd = syscall(SYS_socket, 0x10ul, 0x803ul, 0xcul, 0, 0, 0); >> *(uint32_t*)0x20e64000 = (uint32_t)0x28; >> *(uint32_t*)0x20e64004 = (uint32_t)0x10; >> *(uint64_t*)0x20e64008 = (uint64_t)0x0; >> *(uint64_t*)0x20e64010 = (uint64_t)0x3; >> *(uint64_t*)0x20e64018 = (uint64_t)0xfff; >> *(uint16_t*)0x20e64020 = (uint16_t)0x5; >> syscall(SYS_write, fd, 0x20e64000ul, 0x28ul, 0, 0, 0); >> return 0; >> } > > CONFIG_NETLINK_MMAP and nfnetlink batching strike in unison :-/ > > root cause is in nfnetlink_rcv_batch(): > > 296 replay: > 297 status = 0; > 298 > 299 skb = netlink_skb_clone(oskb, GFP_KERNEL); > > The clone op doesn't copy oskb->sk, so we oops in > __netlink_alloc_skb -> netlink_getsockbyportid() when nfnetlink_rcv_batch > tries to send netlink ack.
If indeed oskb is the mmap'ed netlink skb, then it's not even allowed to call into skb_clone() as it would access skb shared info data that can be controlled by the user space mmap buffer, iirc, we had that in the past with nlmon where skb_clone() was accidentally used.
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