Hi Luiz,
> Hi Mariusz,
>
> On Sun, Jan 21, 2024 at 5:04 AM Mariusz Kozłowski mk@xxxxxxxxxxxx> wrote:
> >
> > Version 3 capability masks are 64 bits in size.
> > ---
> > tools/btmon-logger.c | 12 ++++++------
> > 1 file changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/tools/btmon-logger.c b/tools/btmon-logger.c
> > index a770ad575..1f6db3751 100644
> > --- a/tools/btmon-logger.c
> > +++ b/tools/btmon-logger.c
> > @@ -161,14 +161,14 @@ extern int capset(struct __user_cap_header_struct *header,
> > static void drop_capabilities(void)
> > {
> > struct __user_cap_header_struct header;
> > - struct __user_cap_data_struct cap;
> > + struct __user_cap_data_struct cap[_LINUX_CAPABILITY_U32S_3];
>
> Ok, but this doesn't change the field, it makes it an array, or are
> you talking about the following note:
>
> Note that 64-bit capabilities use datap[0] and datap[1], whereas
> 32-bit capabilities use only datap[0].
>
> In that case Ive just pointed out to this note to explain why this is needed.
For version 3 caps (64 bit masks) a single struct __user_cap_data_struct is not
big enough and capget() writes past the end of cap structure on the stack. To
accomodate version 3 cap masks the cap structure needs to be 2x bigger.
> > unsigned int mask;
> > int err;
> >
> > header.version = _LINUX_CAPABILITY_VERSION_3;
> > header.pid = 0;
> >
> > - err = capget(&header, &cap);
> > + err = capget(&header, cap);
> > if (err) {
> > perror("Unable to get current capabilities");
> > return;
> > @@ -177,11 +177,11 @@ static void drop_capabilities(void)
> > /* not needed anymore since monitor socket is already open */
> > mask = ~CAP_TO_MASK(CAP_NET_RAW);
> >
> > - cap.effective &= mask;
> > - cap.permitted &= mask;
> > - cap.inheritable &= mask;
> > + cap[0].effective &= mask;
> > + cap[0].permitted &= mask;
> > + cap[0].inheritable &= mask;
> >
> > - err = capset(&header, &cap);
> > + err = capset(&header, cap);
> > if (err)
> > perror("Failed to set capabilities");
> > }
> > --
> > 2.34.1
> >
> >
>
>
> --
> Luiz Augusto von Dentz
>
>
