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

[Przemek Kitszel]

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