Date: Fri, 18 Mar 2022 13:02:37 -0500 From: Mike Karels <mike@karels.net> To: freebsd-net@freebsd.org Subject: kernel epoch crash in IPv4 multicast code Message-ID: <202203181802.22II2bvI024961@mail.karels.net>
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It looks like the IPv4 multicast code has not been fully converted to
use epochs. I installed this week's snapshot of -current, configured
and started mrouted, and started rwhod -m. The system crashed shortly
thereafter with this:
panic: Assertion in_epoch(net_epoch_preempt) failed at /usr/src/sys/netine=
t/ip_output.c:343
cpuid =3D 15
time =3D 1647609865
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe01b51a=
39d0
vpanic() at vpanic+0x17f/frame 0xfffffe01b51a3a20
panic() at panic+0x43/frame 0xfffffe01b51a3a80
ip_output() at ip_output+0x15f9/frame 0xfffffe01b51a3b80
phyint_send() at phyint_send+0x107/frame 0xfffffe01b51a3be0
ip_mdq() at ip_mdq+0x259/frame 0xfffffe01b51a3c60
X_ip_mrouter_set() at X_ip_mrouter_set+0x9e4/frame 0xfffffe01b51a3d30
sosetopt() at sosetopt+0xee/frame 0xfffffe01b51a3d80
kern_setsockopt() at kern_setsockopt+0xad/frame 0xfffffe01b51a3de0
sys_setsockopt() at sys_setsockopt+0x24/frame 0xfffffe01b51a3e00
amd64_syscall() at amd64_syscall+0x12e/frame 0xfffffe01b51a3f30
fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe01b51a3f30
--- syscall (105, FreeBSD ELF64, sys_setsockopt), rip =3D 0x821b72dda, rsp=
=3D 0x8204c06f8, rbp =3D 0x8204c0750 ---
KDB: enter: panic
The kgdb backtrace is appended.
It looks like ip_mroute is protected in the forwarding path (it's called
from ip_input) and the output path, but not in the setup path from
setsockopt(). At least the MRT_ADD_MFC call needs to enter an epoch.
I tried adding epoch handling in add_mfc(), and that seems to work.
The alternative would be to do it in Xip_mrouter_set() so it would cover
all the calls. Any opinions?
Mike
(kgdb) bt
#0 __curthread () at /usr/src/sys/amd64/include/pcpu_aux.h:55
#1 doadump (textdump=3Dtextdump@entry=3D1)
at /usr/src/sys/kern/kern_shutdown.c:406
#2 0xffffffff80c0b8ed in kern_reboot (howto=3D260)
at /usr/src/sys/kern/kern_shutdown.c:527
#3 0xffffffff80c0bdfe in vpanic (
fmt=3D0xffffffff8120c2ec "Assertion %s failed at %s:%d", ap=3D<optimiz=
ed out>)
at /usr/src/sys/kern/kern_shutdown.c:965
#4 0xffffffff80c0bb53 in panic (fmt=3D<unavailable>)
at /usr/src/sys/kern/kern_shutdown.c:889
#5 0xffffffff80dde8f9 in ip_output (m=3Dm@entry=3D0xfffff802de8cb000, =
opt=3Dopt@entry=3D0x0, ro=3Dro@entry=3D0x0, flags=3Dflags@entry=3D1, =
imo=3Dimo@entry=3D0xfffffe01b51a3b98, inp=3Dinp@entry=3D0x0)
at /usr/src/sys/netinet/ip_output.c:343
#6 0xffffffff82847317 in send_packet (vifp=3D0xfffff801c8620000, =
m=3D<optimized out>) at /usr/src/sys/netinet/ip_mroute.c:1768
#7 phyint_send (ip=3Dip@entry=3D0xfffff8000ff1fc68, vifp=3D0xfffff801c862=
0000, =
m=3D<optimized out>, m@entry=3D0xfffff8000ff1fc00)
at /usr/src/sys/netinet/ip_mroute.c:1745
#8 0xffffffff828465c9 in ip_mdq (m=3D0xfffff8000ff1fc00, ifp=3D<optimized=
out>, =
rt=3Drt@entry=3D0xfffff80025175b00, xmt_vif=3Dxmt_vif@entry=3D65535)
at /usr/src/sys/netinet/ip_mroute.c:1653
#9 0xffffffff82844924 in add_mfc (mfccp=3D0xfffffe01b51a3ca0)
at /usr/src/sys/netinet/ip_mroute.c:1168
#10 X_ip_mrouter_set (so=3D<optimized out>, =
so@entry=3D<error reading variable: value is not available>, =
sopt=3D<optimized out>, =
sopt@entry=3D<error reading variable: value is not available>)
at /usr/src/sys/netinet/ip_mroute.c:469
#11 0xffffffff80cbbafe in sosetopt (so=3D0xfffff8000fb1d3c0,
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