Re: [9fans] 4th edition file server available

[andrey mirtchovski <andrey@lanl.gov>]

On Mon, 13 Jan 2003, Russ Cox wrote:

> There are no buffer overflows anyway.  ;-)


I see the smiley, but have to reply anyway. this is not a nasty jab
at Russ, just a fix (I hope :)

there's a buffer overflow in cpu.c (strcpy):

% cpu -h `{perl -e '{print "A"x100;}'}
cpu 116986: suicide: sys: trap: fault read addr=0x19000 pc=0x00005b8b
plan9% acid 116986
/proc/116986/text:386 plan 9 executable

/sys/lib/acid/port
/sys/lib/acid/386
acid: stk()
At pc:0x00005b8b:fmtfmt+0x1f /sys/src/libc/fmt/fmt.c:63
fmtfmt(c=0x00000073) /sys/src/libc/fmt/fmt.c:57
        called from _fmtdispatch+0x83 /sys/src/libc/fmt/fmt.c:175
_fmtdispatch(isrunes=0x00000000,f=0x7fffeb48,fmt=0x000168b6) /sys/src/libc/fmt/fmt.c:113
        called from dofmt+0x75 /sys/src/libc/fmt/dofmt.c:62
dofmt(fmt=0x000168b4,f=0x7fffeb48) /sys/src/libc/fmt/dofmt.c:7
        called from vsnprint+0x62 /sys/src/libc/fmt/vsnprint.c:20
vsnprint(len=0x00000100,buf=0x00018734,args=0x7fffebac,fmt=0x000168b0) /sys/src/libc/fmt/vsnprint.c:5
        called from snprint+0x2b /sys/src/libc/fmt/snprint.c:13
snprint(fmt=0x000168b0,buf=0x00018734,len=0x00000100) /sys/src/libc/fmt/snprint.c:5
        called from netmkaddr+0x5e /sys/src/libc/port/netmkaddr.c:34
netmkaddr(linear=0x00017e0c,defnet=0x00000000,defsrv=0x00016978) /sys/src/libc/port/netmkaddr.c:10
        called from rexcall+0x28 /sys/src/cmd/cpu.c:347
rexcall(host=0x00017e0c,service=0x00016978,fd=0x7fffed98) /sys/src/cmd/cpu.c:339
        called from main+0x132 /sys/src/cmd/cpu.c:147
main(argv=0x7fffef84,argc=0x00000000) /sys/src/cmd/cpu.c:77
        called from _main+0x31 /sys/src/libc/386/main9.s:16
acid:


----------------------

here's the fix:

plan9% diff cpu.c /sys/src/cmd/cpu.c
121c121
<               strncpy(system, p, sizeof system);
---
>               strcpy(system, p);
plan9% 8c cpu.c; 8l cpu.8
plan9% 8.out -h `{perl -e '{print "A"x100}'}
cpu: can't dial: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA: cs: can't translate address
plan9%