[PATCH 3/7] tap: Check return value of accept4() before calling getsockopt()

[Stefano Brivio <sbrivio@redhat.com>]

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Reported by Coverity (CWE-119):

	Negative value used as argument to a function expecting a
	positive value (for example, size of buffer or allocation)

and harmless, because getsockopt() would return -EBADF if the
socket is -1, so we wouldn't print anything.

Check if accept4() returns a valid socket before calling getsockopt()
on it.

Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com>
---
 tap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tap.c b/tap.c
index 3231da7..4d7422f 100644
--- a/tap.c
+++ b/tap.c
@@ -872,11 +872,13 @@ static void tap_sock_unix_new(struct ctx *c)
 		int discard = accept4(c->fd_tap_listen, NULL, NULL,
 				      SOCK_NONBLOCK);
 
+		if (discard == -1)
+			return;
+
 		if (!getsockopt(discard, SOL_SOCKET, SO_PEERCRED, &ucred, &len))
 			info("discarding connection from PID %i", ucred.pid);
 
-		if (discard != -1)
-			close(discard);
+		close(discard);
 
 		return;
 	}
-- 
@@ -872,11 +872,13 @@ static void tap_sock_unix_new(struct ctx *c)
 		int discard = accept4(c->fd_tap_listen, NULL, NULL,
 				      SOCK_NONBLOCK);
 
+		if (discard == -1)
+			return;
+
 		if (!getsockopt(discard, SOL_SOCKET, SO_PEERCRED, &ucred, &len))
 			info("discarding connection from PID %i", ucred.pid);
 
-		if (discard != -1)
-			close(discard);
+		close(discard);
 
 		return;
 	}
-- 
2.35.1