On Tue, Jul 29, 2025 at 08:02:25AM +0200, Thomas Huth wrote:
> On 28/07/2025 19.53, Daniel P. Berrangé wrote:
> > On Mon, Jul 28, 2025 at 07:30:16PM +0200, Thomas Huth wrote:
> > > From: Thomas Huth <th...@redhat.com>
> > >
> > > When compiling QEMU with --enable-ubsan there is a undefined behavior
> > > warning when running "make check":
> > >
> > > .../qga/commands-linux.c:452:15: runtime error: applying non-zero
> > > offset 5 to null pointer
> > > #0 0x55ea7b89450c in build_guest_fsinfo_for_pci_dev
> > > ..../qga/commands-linux.c:452:15
> > >
> > > Add a check to avoid incrementing the NULL pointer here.
> > >
> > > Signed-off-by: Thomas Huth <th...@redhat.com>
> > > ---
> > > qga/commands-linux.c | 4 +++-
> > > 1 file changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/qga/commands-linux.c b/qga/commands-linux.c
> > > index 9e8a934b9a6..caf7c3ca22b 100644
> > > --- a/qga/commands-linux.c
> > > +++ b/qga/commands-linux.c
> > > @@ -449,7 +449,9 @@ static bool build_guest_fsinfo_for_pci_dev(char const
> > > *syspath,
> > > has_ata = true;
> > > } else {
> > > p = strstr(syspath, "/host");
> > > - q = p + 5;
> > > + if (p) {
> > > + q = p + 5;
> > > + }
> > > }
> > > if (p && sscanf(q, "%u", &host) == 1) {
> >
> > q is always non-NULL if p is non-NULL, so this is safe, but I would be more
> > happy with this changing to 'q && sscanf' to eliminate the indirection.
>
> If we agree to do a bigger change here, I'd rather drop the "q" pointer
> completely and use a new integer variable instead, something like:
>
> int offset;
> ...
> p = strstr(syspath, "/ata");
> if (p) {
> offset = 4;
> has_ata = true;
> } else {
> offset = 5;
> p = strstr(syspath, "/host");
> }
> if (p && sscanf(p + offset, "%u", &host) == 1) {
> ...
> }
>
> WDYT?
Works for me.
With regards,
Daniel
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