Re: Panic: Memory modified after free

On 7/22/26 10:01, Steve Kargl wrote:
> Just received the following panic.  I was using openvpn at the time of
> the panic.  If I look at core.txt.2, I see
> 
> 
> Tue Jul 21 20:51:38 PDT 2026
> Jul 22 08:47:37 hotrats su[4849]: kargl to root on /dev/pts/3
> ovpn0: changing name to 'tun0'
> tun0: link state changed to UP
> Jul 22 08:48:45 hotrats openvpn[4908]: event_wait : Interrupted system 
> call (fd=-1,code=4)
> ovpn0: changing name to 'tun0'
> tun0: link state changed to UP
> Jul 22 09:27:42 hotrats openvpn[5673]: event_wait : Interrupted system 
> call (fd=-1,code=4)
> panic: Memory modified after free 0xfffff8037d3a3300 (256, mbuf) + 8 = 
> deadc0dedead40ce
> 
> cpuid = 7
> time = 1784737711
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 
> 0xfffffe01498028f0
> vpanic() at vpanic+0x136/frame 0xfffffe0149802a20
> panic() at panic+0x43/frame 0xfffffe0149802a80
> trash_ctor() at trash_ctor+0x74/frame 0xfffffe0149802a90
> item_ctor() at item_ctor+0x59/frame 0xfffffe0149802ae0
> mc_get() at mc_get+0x14c/frame 0xfffffe0149802b40
> mc_uiotomc() at mc_uiotomc+0x8d/frame 0xfffffe0149802b80
> uipc_sosend_stream_or_seqpacket() at 
> uipc_sosend_stream_or_seqpacket+0x13e/frame 0xfffffe0149802c60
> sousrsend() at sousrsend+0x79/frame 0xfffffe0149802cc0
> kern_sendit() at kern_sendit+0x1be/frame 0xfffffe0149802d50
> sendit() at sendit+0x1ab/frame 0xfffffe0149802da0
> sys_sendmsg() at sys_sendmsg+0x5b/frame 0xfffffe0149802e00
> amd64_syscall() at amd64_syscall+0x169/frame 0xfffffe0149802f30
> fast_syscall_common() at fast_syscall_common+0xf8/frame 0xfffffe0149802f30
> --- syscall (28, FreeBSD ELF64, sendmsg), rip = 0x39727abfe3ca, rsp = 
> 0x397275edc298, rbp = 0x397275edc2c0 ---
> KDB: enter: panic
> 
> I have crash dump and can upload to kargl@freefall if needed.
> 

Additional info.

%  uname -a
FreeBSD hotrats 16.0-CURRENT FreeBSD 16.0-CURRENT #0 
main-n284956-de9fe28ab847: Fri Apr 10 10:15:09 PDT 2026 
kargl@hotrats:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64

I'm using the 4BSD kernel.

-- 
steve