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[PULL for-5.0 4/5] qga: Fix undefined C behavior
From: |
Michael Roth |
Subject: |
[PULL for-5.0 4/5] qga: Fix undefined C behavior |
Date: |
Tue, 24 Mar 2020 11:46:52 -0500 |
From: Eric Blake <address@hidden>
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 <address@hidden>
Fixes: 0b4b49387
Fixes: Coverity CID 1421990
Signed-off-by: Eric Blake <address@hidden>
Signed-off-by: Michael Roth <address@hidden>
---
qga/commands.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
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:
--
2.17.1
- [PULL for-5.0 0/5] qemu-ga patch queue for hard-freeze, Michael Roth, 2020/03/24
- [PULL for-5.0 2/5] qga-win: Handle VSS_E_PROVIDER_ALREADY_REGISTERED error, Michael Roth, 2020/03/24
- [PULL for-5.0 3/5] qga-win: prevent crash when executing guest-file-read with large count, Michael Roth, 2020/03/24
- [PULL for-5.0 4/5] qga: Fix undefined C behavior,
Michael Roth <=
- [PULL for-5.0 5/5] qemu-ga: document vsock-listen in the man page, Michael Roth, 2020/03/24
- [PULL for-5.0 1/5] qga: Installer: Wait for installation to finish, Michael Roth, 2020/03/24
- Re: [PULL for-5.0 0/5] qemu-ga patch queue for hard-freeze, Peter Maydell, 2020/03/24