Re: [PATCH RESEND] ptp: Fixes a null pointer dereference in ptp_ioctl

[Przemek Kitszel]

On 11/8/23 11:15, Przemek Kitszel wrote:
> On 11/7/23 21:48, Yuran Pereira wrote:
> > Syzkaller found a null pointer dereference in ptp_ioctl

Ugh, I just noticed that this is a fixed version of previous attempt,
for those please always bump version and include changelog, please
also comply with:
https://www.kernel.org/doc/html/next/process/maintainer-netdev.html

if only to don't fool random reviewers
(I somewhat assumed that you have just rebased some old patch,
PATCH RESEND was misleading here)

> > originating from the lack of a null check for tsevq.
> >
> > ```
> > general protection fault, probably for non-canonical
> >     address 0xdffffc000000020b: 0000 [#1] PREEMPT SMP KASAN
> > KASAN: probably user-memory-access in range
> >     [0x0000000000001058-0x000000000000105f]
> > CPU: 0 PID: 5053 Comm: syz-executor353 Not tainted
> >     6.6.0-syzkaller-10396-g4652b8e4f3ff #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine,
> >     BIOS Google 10/09/2023
> > RIP: 0010:ptp_ioctl+0xcb7/0x1d10 drivers/ptp/ptp_chardev.c:476
> > ...
> > Call Trace:
> >   <TASK>
> >   posix_clock_ioctl+0xf8/0x160 kernel/time/posix-clock.c:86
> >   vfs_ioctl fs/ioctl.c:51 [inline]
> >   __do_sys_ioctl fs/ioctl.c:871 [inline]
> >   __se_sys_ioctl fs/ioctl.c:857 [inline]
> >   __x64_sys_ioctl+0x18f/0x210 fs/ioctl.c:857
> >   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
> >   do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
> >   entry_SYSCALL_64_after_hwframe+0x63/0x6b
> > ```
> >
> > This patch fixes the issue by adding a check for tsevq and
> > ensuring ptp_ioctl returns with an error if tsevq is null.
> >
> > Reported-by: syzbot+8a78ecea7ac1a2ea26e5@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Closes: https://syzkaller.appspot.com/bug?extid=8a78ecea7ac1a2ea26e5
> > Fixes: c5a445b1e934 ("ptp: support event queue reader channel masks")
> > Signed-off-by: Yuran Pereira <yuran.pereira@xxxxxxxxxxx>
> > ---
> >   drivers/ptp/ptp_chardev.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
> > index 282cd7d24077..5b36c34629a0 100644
> > --- a/drivers/ptp/ptp_chardev.c
> > +++ b/drivers/ptp/ptp_chardev.c
> > @@ -173,6 +173,8 @@ long ptp_ioctl(struct posix_clock_context 
> > *pccontext, unsigned int cmd,
> >       int enable, err = 0;
> >       tsevq = pccontext->private_clkdata;
> > +    if (!tsevq)
> > +        return -EINVAL;
> >       switch (cmd) {
>
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>

Still applies, code is fine, thanks!