hw/misc/ivshmem-pci: Improve error handling

Coverity points out that the ivshmem-pci code has some error handling
cases where it incorrectly tries to use an invalid filedescriptor.
These generally happen because ivshmem_recv_msg() calls
qemu_chr_fe_get_msgfd(), which might return -1, but the code in
process_msg() generally assumes that the file descriptor was provided
when it was supposed to be. In particular:
 * the error case in process_msg() only needs to close the fd
   if one was provided
 * process_msg_shmem() should fail if no fd was provided

Coverity: CID 1508726
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20250711145012.1521936-1-peter.maydell@linaro.org

1 files changed, 8 insertions, 1 deletions

diff --git a/hw/misc/ivshmem-pci.c b/hw/misc/ivshmem-pci.c
index 5a10bca633..d47ae739d6 100644
--- a/hw/misc/ivshmem-pci.c
+++ b/hw/misc/ivshmem-pci.c
@@ -479,6 +479,11 @@ static void process_msg_shmem(IVShmemState *s, int fd, Error **errp)
     struct stat buf;
     size_t size;
 
+    if (fd < 0) {
+        error_setg(errp, "server didn't provide fd with shared memory message");
+        return;
+    }
+
     if (s->ivshmem_bar2) {
         error_setg(errp, "server sent unexpected shared memory message");
         close(fd);
@@ -553,7 +558,9 @@ static void process_msg(IVShmemState *s, int64_t msg, int fd, Error **errp)
 
     if (msg < -1 || msg > IVSHMEM_MAX_PEERS) {
         error_setg(errp, "server sent invalid message %" PRId64, msg);
-        close(fd);
+        if (fd >= 0) {
+            close(fd);
+        }
         return;
     }