[Spice-devel] [linux/vd_agent v1 2/2] covscan: avoid false positive on g_clear_pointer()
Victor Toso
victortoso at redhat.com
Tue Aug 27 10:13:58 UTC 2019
From: Victor Toso <me at victortoso.com>
This is a CLANG_WARNING found by covscan. It is a false positive as
g_clear_pointer() does set vportp to NULL, meaning that the situation
described by covscan below should not be reached. Moving away from
g_clear_pointer() in this specific case just to make our tool happy.
Covscan report:
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:458:9: warning: Use of memory after it is freed
> # if (wbuf->write_pos != wbuf->size) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:268:12: note: Assuming the condition is true
> # while (*vportp && (*vportp)->write_buf)
> # ^~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:268:12: note: Left side of '&&' is true
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:268:5: note: Loop condition is true. Entering loop body
> # while (*vportp && (*vportp)->write_buf)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:269:9: note: Calling 'vdagent_virtio_port_do_write'
> # vdagent_virtio_port_do_write(vportp);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:453:5: note: Taking false branch
> # if (!wbuf) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:458:9: note: Assuming the condition is false
> # if (wbuf->write_pos != wbuf->size) {
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:458:5: note: Taking false branch
> # if (wbuf->write_pos != wbuf->size) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:465:9: note: Assuming 'n' is < 0
> # if (n < 0) {
> # ^~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:465:5: note: Taking true branch
> # if (n < 0) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:466:13: note: Assuming the condition is false
> # if (errno == EINTR)
> # ^~~~~~~~~~~~~~
> /usr/include/errno.h:38:16: note: expanded from macro 'errno'
> ## define errno (*__errno_location ())
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:466:9: note: Taking false branch
> # if (errno == EINTR)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:469:9: note: Calling 'vdagent_virtio_port_destroy'
> # vdagent_virtio_port_destroy(vportp);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:130:5: note: Taking false branch
> # if (!vport)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:133:9: note: Assuming the condition is false
> # if (vport->disconnect_callback)
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:133:5: note: Taking false branch
> # if (vport->disconnect_callback)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:137:5: note: Loop condition is true. Entering loop body
> # while (wbuf) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:140:9: note: Memory is released
> # g_free(wbuf);
> # ^~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:137:5: note: Loop condition is false. Execution continues on line 144
> # while (wbuf) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:144:5: note: Loop condition is true. Entering loop body
> # for (i = 0; i < VDP_END_PORT; i++) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:144:5: note: Loop condition is true. Entering loop body
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:144:5: note: Loop condition is true. Entering loop body
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:144:5: note: Loop condition is false. Execution continues on line 148
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:149:5: note: Assuming '_p' is null
> # g_clear_pointer(vportp, g_free);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /usr/include/glib-2.0/glib/gmem.h:124:9: note: expanded from macro 'g_clear_pointer'
> # if (_p) \
> # ^~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:149:5: note: Taking false branch
> /usr/include/glib-2.0/glib/gmem.h:124:5: note: expanded from macro 'g_clear_pointer'
> # if (_p) \
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:149:5: note: Loop condition is false. Exiting loop
> /usr/include/glib-2.0/glib/gmem.h:114:3: note: expanded from macro 'g_clear_pointer'
> # G_STMT_START { \
> # ^
> /usr/include/glib-2.0/glib/gmacros.h:346:23: note: expanded from macro 'G_STMT_START'
> ##define G_STMT_START do
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:469:9: note: Returning; memory was released
> # vdagent_virtio_port_destroy(vportp);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:269:9: note: Returning; memory was released
> # vdagent_virtio_port_do_write(vportp);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:268:12: note: Left side of '&&' is true
> # while (*vportp && (*vportp)->write_buf)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:268:5: note: Loop condition is true. Entering loop body
> # while (*vportp && (*vportp)->write_buf)
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:269:9: note: Calling 'vdagent_virtio_port_do_write'
> # vdagent_virtio_port_do_write(vportp);
> # ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:453:5: note: Taking false branch
> # if (!wbuf) {
> # ^
> spice-vdagent-0.19.0/src/vdagentd/virtio-port.c:458:9: note: Use of memory after it is freed
> # if (wbuf->write_pos != wbuf->size) {
> # ^~~~~~~~~~~~~~~
> # 456| }
> # 457|
> # 458|-> if (wbuf->write_pos != wbuf->size) {
> # 459| syslog(LOG_ERR, "do_write: buffer is incomplete!!");
> # 460| return;
Signed-off-by: Victor Toso <victortoso at redhat.com>
---
src/vdagentd/virtio-port.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/src/vdagentd/virtio-port.c b/src/vdagentd/virtio-port.c
index b0556ce..3ae7f22 100644
--- a/src/vdagentd/virtio-port.c
+++ b/src/vdagentd/virtio-port.c
@@ -146,7 +146,8 @@ void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
}
close(vport->fd);
- g_clear_pointer(vportp, g_free);
+ g_free(vport);
+ *vportp = NULL;
}
int vdagent_virtio_port_fill_fds(struct vdagent_virtio_port *vport,
--
2.21.0
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