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SubjectRe: [PATCH 3.18 08/20] tun/tap: sanitize TUNSETSNDBUF input
On Thu, Nov 16, 2017 at 12:28 PM, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> 3.18-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Craig Gallek <kraig@google.com>
>
>
> [ 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@google.com>
> Reviewed-by: Eric Dumazet <edumazet@google.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
> 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.

>
> q->sk.sk_sndbuf = u;
> return 0;
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2054,6 +2054,10 @@ static long __tun_chr_ioctl(struct file
> ret = -EFAULT;
> break;
> }
> + if (sndbuf <= 0) {
> + ret = -EINVAL;
> + break;
> + }
>
> tun->sndbuf = sndbuf;
> tun_set_sndbuf(tun);
>
>
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