udp_peek_addr() initialises struct msghdr without setting msg_iov,
leaving it implicitly NULL. Coverity flags this as FORWARD_NULL,
believing recvmsg() will dereference the NULL pointer.
In practice, msg_iovlen being zero means the kernel never touches
msg_iov, so the warning is a false positive. We now provide a
one-byte dummy iov to make msg_iov non-NULL, hence suppressing this
warning without changing the function's behaviour.
Signed-off-by: Jon Maloy
----
v2: - Make the dummy iov conditional on an ANALYZER macro, so it has
zero runtime cost in production builds.
- Add a new 'analyzer' Makefile target (similar to 'valgrind')
that defines ANALYZER via CPPFLAGS for use with static analysis
builds.
---
Makefile | 3 +++
udp.c | 11 +++++++++++
2 files changed, 14 insertions(+)
diff --git a/Makefile b/Makefile
index 0a0a60b0..4dcf4cd1 100644
--- a/Makefile
+++ b/Makefile
@@ -122,6 +122,9 @@ passt-repair: $(PASST_REPAIR_SRCS) $(PASST_REPAIR_HEADERS) seccomp_repair.h
pesto: BASE_CPPFLAGS += -DPESTO
pesto: $(PESTO_SRCS) $(PESTO_HEADERS) seccomp_pesto.h
+analyzer: BASE_CPPFLAGS += -DANALYZER
+analyzer: all
+
valgrind: EXTRA_SYSCALLS += rt_sigprocmask rt_sigtimedwait rt_sigaction \
rt_sigreturn getpid gettid kill clock_gettime \
mmap|mmap2 munmap open unlink gettimeofday futex \
diff --git a/udp.c b/udp.c
index c28d6ee2..36c8c070 100644
--- a/udp.c
+++ b/udp.c
@@ -734,9 +734,20 @@ static int udp_peek_addr(int s, union sockaddr_inany *src,
{
char sastr[SOCKADDR_STRLEN], dstr[INANY_ADDRSTRLEN];
char cmsg[PKTINFO_SPACE];
+#ifdef ANALYZER
+ char dummy;
+ struct iovec iov = {
+ .iov_base = &dummy,
+ .iov_len = sizeof(dummy),
+ };
+#endif /* ANALYZER */
struct msghdr msg = {
.msg_name = src,
.msg_namelen = sizeof(*src),
+#ifdef ANALYZER
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+#endif /* ANALYZER */
.msg_control = cmsg,
.msg_controllen = sizeof(cmsg),
};
--
2.52.0