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Subject[PATCH 4.13 35/44] tun/tap: sanitize TUNSETSNDBUF input
Date
4.13-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/tap.c | 2 ++
drivers/net/tun.c | 4 ++++
2 files changed, 6 insertions(+)

--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -1035,6 +1035,8 @@ static long tap_ioctl(struct file *file,
case TUNSETSNDBUF:
if (get_user(s, sp))
return -EFAULT;
+ if (s <= 0)
+ return -EINVAL;

q->sk.sk_sndbuf = s;
return 0;
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2219,6 +2219,10 @@ 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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