John Hubbard wrote:
> When building with clang, via:
>
> make LLVM=1 -C tools/testing/selftest
>
> ...clang warns about three variables that are not initialized in all
> cases:
>
> 1) The opt_ipproto_off variable is used uninitialized if "testname" is
> not "ip". This seems like an actual bug.
>
> 2) The addr_len is used uninitialized, but only in the assert case,
> which bails out, so this is harmless.
>
> 3) The family variable in add_listener() is only used uninitialized in
> the error case (neither IPv4 nor IPv6 is specified), so it's also
> harmless.
>
> Fix by initializing each variable.
>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
> tools/testing/selftests/net/gro.c | 3 ++-
> tools/testing/selftests/net/ip_local_port_range.c | 2 +-
> tools/testing/selftests/net/mptcp/pm_nl_ctl.c | 2 +-
> 3 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/tools/testing/selftests/net/gro.c b/tools/testing/selftests/net/gro.c
> index 353e1e867fbb..0eb61edaad83 100644
> --- a/tools/testing/selftests/net/gro.c
> +++ b/tools/testing/selftests/net/gro.c
> @@ -110,7 +110,8 @@ static void setup_sock_filter(int fd)
> const int dport_off = tcp_offset + offsetof(struct tcphdr, dest);
> const int ethproto_off = offsetof(struct ethhdr, h_proto);
> int optlen = 0;
> - int ipproto_off, opt_ipproto_off;
> + int ipproto_off;
> + int opt_ipproto_off = 0;
This is only intended to be used in the case where the IP proto is not TCP:
BPF_STMT(BPF_LD + BPF_B + BPF_ABS, ipproto_off),
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 2, 0),
+ BPF_STMT(BPF_LD + BPF_B + BPF_ABS, opt_ipproto_off),
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_TCP, 0, 5),
In that case the test tries again at a different offset that accounts
for optional IPv6 extension headers.
This is indeed buggy, in that it might accidentally accept packets
that should be dropped.
Initializing to 0 compares against against the first byte of the
Ethernet header. Which is an external argument to the test. So
safest is to initialize opt_ipproto_off to ipproto_off and just
repeat the previous check. Perhaps:
@@ -118,6 +118,7 @@ static void setup_sock_filter(int fd)
else
next_off = offsetof(struct ipv6hdr, nexthdr);
ipproto_off = ETH_HLEN + next_off;
+ opt_ipproto_off = ipproto_off; /* overridden later if may have exthdrs */
