On 03/23/2017 08:31 AM, Marc-André Lureau wrote:
ASAN detects an "unknown-crash" when running pxe-test:
/ppc64/pxe/spapr-vlan:
=================================================================
==7143==ERROR: AddressSanitizer: unknown-crash on address 0x7f6dcd298d30 at pc
0x55e22218830d bp 0x7f6dcd2989e0 sp 0x7f6dcd2989d0
READ of size 128 at 0x7f6dcd298d30 thread T2
#0 0x55e22218830c in tftp_session_allocate
/home/elmarco/src/qq/slirp/tftp.c:73
#1 0x55e22218a1f8 in tftp_handle_rrq /home/elmarco/src/qq/slirp/tftp.c:289
#2 0x55e22218b54c in tftp_input /home/elmarco/src/qq/slirp/tftp.c:446
#3 0x55e2221833fe in udp6_input /home/elmarco/src/qq/slirp/udp6.c:82
Interesting bug, udp6.c seems to have been started as a copy of udp.c,
which uses:
struct sockaddr_storage lhost;
struct sockaddr_in *lhost4;
but in udp6.c this was changed to:
struct sockaddr_in6 lhost;
tftp_session_allocate() behavior was fine with IPv4 but dual-stack broke it.
Your fix uses sockaddr_size() which is the cleaner/safer way to do it
but I'm wondering how to avoid such dual-stack sockaddr issues before
runtime ASAN spotting.
One way can be to use 'union slirp_sockaddr' recently extracted by Dave
Gilbert (see http://patchwork.ozlabs.org/patch/746605), it uses more
stack but this avoid partial underflows.
#4 0x55e222137b17 in ip6_input /home/elmarco/src/qq/slirp/ip6_input.c:67
Address 0x7f6dcd298d30 is located in stack of thread T2 at offset 96 in frame
#0 0x55e222182420 in udp6_input /home/elmarco/src/qq/slirp/udp6.c:13
This frame has 3 object(s):
[32, 48) '<unknown>'
[96, 124) 'lhost' <== Memory access at offset 96 partially overflows this
variable
[160, 200) 'save_ip' <== Memory access at offset 96 partially underflows
this variable
The sockaddr_storage pointer is the sockaddr_in6 lhost on the
stack. Copy only the source addr size.
Signed-off-by: Marc-André Lureau <marcandre.lur...@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
---
slirp/tftp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/slirp/tftp.c b/slirp/tftp.c
index 50e714807d..a9bc4bb1b6 100644
--- a/slirp/tftp.c
+++ b/slirp/tftp.c
@@ -70,7 +70,7 @@ static int tftp_session_allocate(Slirp *slirp, struct
sockaddr_storage *srcsas,
found:
memset(spt, 0, sizeof(*spt));
- spt->client_addr = *srcsas;
+ memcpy(&spt->client_addr, srcsas, sockaddr_size(srcsas));
spt->fd = -1;
spt->block_size = 512;
spt->client_port = tp->udp.uh_sport;
