From 9faaa92e30bcf17b8b2a32607d53f7c8005fd7db Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Petr=20=C5=A0tetiar?= Date: Tue, 29 Oct 2019 21:11:38 +0100 Subject: silence use after the free clang analyzer warning MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit scan-build from clang version 9 complains about following: nl.c:507:9: warning: Use of memory after it is freed while (nlmsg_ok(hdr, n)) { ^~~~~~~~~~~~~~~~ which seems to be impossible codepath as clang analyzer doesn't somehow account properly nl_syserr2nlerr(errno) return value: } else { free(msg.msg_control); free(*buf); return -nl_syserr2nlerr(errno); } which should be always < 0, but analyzer is still checking for > 0 code path as well for some reason. So in order to make the analyzer happy, set the buf pointer to NULL explicitly and add assert to make it clear, that this codepath should never happen. Signed-off-by: Petr Štetiar --- nl.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'nl.c') diff --git a/nl.c b/nl.c index 2649470..505965f 100644 --- a/nl.c +++ b/nl.c @@ -400,7 +400,9 @@ int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla, page_size = getpagesize() * 4; iov.iov_len = page_size; - iov.iov_base = *buf = malloc(iov.iov_len); + iov.iov_base = *buf = calloc(1, iov.iov_len); + if (!*buf) + return -nl_syserr2nlerr(errno); if (sk->s_flags & NL_SOCK_PASSCRED) { msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred)); @@ -421,6 +423,7 @@ retry: } else { free(msg.msg_control); free(*buf); + *buf = NULL; return -nl_syserr2nlerr(errno); } } @@ -445,6 +448,7 @@ retry: if (msg.msg_namelen != sizeof(struct sockaddr_nl)) { free(msg.msg_control); free(*buf); + *buf = NULL; return -NLE_NOADDR; } @@ -463,6 +467,7 @@ retry: abort: free(msg.msg_control); free(*buf); + *buf = NULL; return 0; } @@ -501,6 +506,9 @@ continue_reading: if (n <= 0) return n; + /* make clang analyzer happy */ + assert(n > 0 && buf); + NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", sk, n); hdr = (struct nlmsghdr *) buf; -- cgit v1.2.1