Re: [PATCH 3.18 08/20] tun/tap: sanitize TUNSETSNDBUF input

[Greg Kroah-Hartman]

On Thu, Nov 16, 2017 at 04:25:13PM -0500, Craig Gallek wrote:
> On Thu, Nov 16, 2017 at 12:28 PM, Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > 3.18-stable review patch.  If anyone has any objections, please let me know.
> >
> > ------------------
> >
> > From: Craig Gallek <kraig@xxxxxxxxxx>
> >
> >
> > [ Upstream commit 93161922c658c714715686cd0cf69b090cb9bf1d ]
> >
> > Syzkaller found several variants of the lockup below by setting negative
> > values with the TUNSETSNDBUF ioctl.  This patch adds a sanity check
> > to both the tun and tap versions of this ioctl.
> >
> >   watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [repro:2389]
> >   Modules linked in:
> >   irq event stamp: 329692056
> >   hardirqs last  enabled at (329692055): [<ffffffff824b8381>] _raw_spin_unlock_irqrestore+0x31/0x75
> >   hardirqs last disabled at (329692056): [<ffffffff824b9e58>] apic_timer_interrupt+0x98/0xb0
> >   softirqs last  enabled at (35659740): [<ffffffff824bc958>] __do_softirq+0x328/0x48c
> >   softirqs last disabled at (35659731): [<ffffffff811c796c>] irq_exit+0xbc/0xd0
> >   CPU: 0 PID: 2389 Comm: repro Not tainted 4.14.0-rc7 #23
> >   Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> >   task: ffff880009452140 task.stack: ffff880006a20000
> >   RIP: 0010:_raw_spin_lock_irqsave+0x11/0x80
> >   RSP: 0018:ffff880006a27c50 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff10
> >   RAX: ffff880009ac68d0 RBX: ffff880006a27ce0 RCX: 0000000000000000
> >   RDX: 0000000000000001 RSI: ffff880006a27ce0 RDI: ffff880009ac6900
> >   RBP: ffff880006a27c60 R08: 0000000000000000 R09: 0000000000000000
> >   R10: 0000000000000001 R11: 000000000063ff00 R12: ffff880009ac6900
> >   R13: ffff880006a27cf8 R14: 0000000000000001 R15: ffff880006a27cf8
> >   FS:  00007f4be4838700(0000) GS:ffff88000cc00000(0000) knlGS:0000000000000000
> >   CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> >   CR2: 0000000020101000 CR3: 0000000009616000 CR4: 00000000000006f0
> >   Call Trace:
> >    prepare_to_wait+0x26/0xc0
> >    sock_alloc_send_pskb+0x14e/0x270
> >    ? remove_wait_queue+0x60/0x60
> >    tun_get_user+0x2cc/0x19d0
> >    ? __tun_get+0x60/0x1b0
> >    tun_chr_write_iter+0x57/0x86
> >    __vfs_write+0x156/0x1e0
> >    vfs_write+0xf7/0x230
> >    SyS_write+0x57/0xd0
> >    entry_SYSCALL_64_fastpath+0x1f/0xbe
> >   RIP: 0033:0x7f4be4356df9
> >   RSP: 002b:00007ffc18101c08 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
> >   RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f4be4356df9
> >   RDX: 0000000000000046 RSI: 0000000020101000 RDI: 0000000000000005
> >   RBP: 00007ffc18101c40 R08: 0000000000000001 R09: 0000000000000001
> >   R10: 0000000000000001 R11: 0000000000000293 R12: 0000559c75f64780
> >   R13: 00007ffc18101d30 R14: 0000000000000000 R15: 0000000000000000
> >
> > Fixes: 33dccbb050bb ("tun: Limit amount of queued packets per device")
> > Fixes: 20d29d7a916a ("net: macvtap driver")
> > Signed-off-by: Craig Gallek <kraig@xxxxxxxxxx>
> > Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> >  drivers/net/macvtap.c |    2 ++
> >  drivers/net/tun.c     |    4 ++++
> >  2 files changed, 6 insertions(+)
> >
> > --- a/drivers/net/macvtap.c
> > +++ b/drivers/net/macvtap.c
> > @@ -1047,6 +1047,8 @@ static long macvtap_ioctl(struct file *f
> >         case TUNSETSNDBUF:
> >                 if (get_user(u, up))
> >                         return -EFAULT;
> > +               if (s <= 0)
> > +                       return -EINVAL;
> Yay build bot!  This 's' should be a 'u' in the 3.18 version.

Yes, that was a good catch, I'll go fix this up, thanks.

greg k-h