[PATCH v6] net/tap-linux.c: avoid abort when setting invalid fd

["Houqi (Nick) Zuo" <hzuo@redhat.com>]

This patch removes abort() call in the tap_fd_set_vnet_hdr_len()
function. If the fd is found to be in a bad state (e.g., EBADFD
 or ENODEV), the function will print an error message.

When QEMU creates a tap device automatically and the tap device is
manually removed from the host while the guest is running, the tap
device file descriptor becomes invalid. Later, when the guest executes
shutdown, the tap_fd_set_vnet_hdr_len() function may be called and
abort QEMU with a core dump when attempting to use the invalid fd.
The expected behavior for this negative test case is that QEMU should
report an error but continue running rather than aborting.

Testing:
- Start QEMU with automatically created tap device
- Manually remove the tap device on the host
- Execute shutdown in the guest
- Verify QEMU reports an error but does not abort

Fixes: 0caed25cd171 ("virtio: Call set_features during reset")
Signed-off-by: Houqi (Nick) Zuo <hzuo@redhat.com>
---
 net/tap-linux.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/tap-linux.c b/net/tap-linux.c
index 2a90b58467..922684f349 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -214,10 +214,11 @@ bool tap_probe_has_tunnel(int fd)
 
 void tap_fd_set_vnet_hdr_len(int fd, int len)
 {
-    if (ioctl(fd, TUNSETVNETHDRSZ, &len) == -1) {
-        fprintf(stderr, "TUNSETVNETHDRSZ ioctl() failed: %s. Exiting.\n",
-                strerror(errno));
-        abort();
+    int ret;
+
+    ret = ioctl(fd, TUNSETVNETHDRSZ, &len);
+    if (ret != 0) {
+        error_report("TUNSETVNETHDRSZ ioctl() failed: %s.", strerror(errno));
     }
 }
 
-- 
2.47.3