From a23f38a72921fa915536a981a4f8a9134512f120 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Fri, 20 Mar 2020 10:05:07 -0500 Subject: qga: Fix undefined C behavior The QAPI struct GuestFileWhence has a comment about how we are exploiting equivalent values between two different integer types shared in a union. But C says behavior is undefined on assignments to overlapping storage when the two types are not the same width, and indeed, 'int64_t value' and 'enum QGASeek name' are very likely to be different in width. Utilize a temporary variable to fix things. Reported-by: Peter Maydell Fixes: 0b4b49387 Fixes: Coverity CID 1421990 Signed-off-by: Eric Blake Signed-off-by: Michael Roth --- qga/commands.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'qga/commands.c') diff --git a/qga/commands.c b/qga/commands.c index f8852beb9c..4471a9f08d 100644 --- a/qga/commands.c +++ b/qga/commands.c @@ -482,10 +482,15 @@ done: * the guest's SEEK_ constants. */ int ga_parse_whence(GuestFileWhence *whence, Error **errp) { - /* Exploit the fact that we picked values to match QGA_SEEK_*. */ + /* + * Exploit the fact that we picked values to match QGA_SEEK_*; + * however, we have to use a temporary variable since the union + * members may have different size. + */ if (whence->type == QTYPE_QSTRING) { + int value = whence->u.name; whence->type = QTYPE_QNUM; - whence->u.value = whence->u.name; + whence->u.value = value; } switch (whence->u.value) { case QGA_SEEK_SET: -- cgit v1.2.3