Messages in this thread | | | Date | Sat, 30 Aug 2008 21:59:38 +0200 | From | "Vegard Nossum" <> | Subject | Re: buffer overflow in /proc/sys/sunrpc/transports |
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On Sat, Aug 30, 2008 at 9:56 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote: > | BTW, look at this: > | > | $ od -A x -t x1z /proc/sys/sunrpc/transports > | 000000 74 63 70 20 31 30 34 38 35 37 36 0a 75 64 70 20 >tcp 1048576.udp < > | 000010 33 32 37 36 38 0a 00 00 00 00 00 00 00 00 00 00 >32768...........< > | 000020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >................< > | * > | 0003e0 00 00 00 00 00 00 00 00 00 00 >..........< > | 0003ea > | > | ...and: > | > | $ strace -e trace=read cat /proc/sys/sunrpc/transports > /dev/null > | read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0@G\316E4\0\0\0"..., > | 512) = 512 > | read(3, "tcp 1048576\nudp 32768\n\0\0\0\0\0\0\0\0\0\0"..., 4096) = 4074 > | read(3, "", 4096) = 0 > | > | ...why does it have a huge return value? The output is only about 40 > | bytes... why add all the \0? Would your patch also fix this? > > I think it's from strace side - it pass 4096 zero'ed buffer.
"cat" passed buffer of size 4096, yes. But read() still returned 4074. It should have returned 38 or so.
> At least I don't see additional issues from kernel side in buffer > filling - except from svc_print_xprts() which walk over list. > But I think sunpc guys should know details :) > Will send short-fix patch soon :)
It looks like it's returning (sizeof(buffer) - x) where it really should be returning x. Maybe it's this one that should be different?
*lenp -= len;
Vegard
-- "The animistic metaphor of the bug that maliciously sneaked in while the programmer was not looking is intellectually dishonest as it disguises that the error is the programmer's own creation." -- E. W. Dijkstra, EWD1036
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