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Message-ID: <91952d00df215751cbc0e4846c2d688f964fbfc1.camel@redhat.com>
Date: Thu, 23 Jun 2022 11:13:41 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Duoming Zhou <duoming@....edu.cn>, linux-hams@...r.kernel.org
Cc: ralf@...ux-mips.org, davem@...emloft.net, edumazet@...gle.com,
kuba@...nel.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 1/2] net: rose: fix UAF bugs caused by timer handler
On Wed, 2022-06-22 at 12:01 +0800, Duoming Zhou wrote:
> There are UAF bugs in rose_heartbeat_expiry(), rose_timer_expiry()
> and rose_idletimer_expiry(). The root cause is that del_timer()
> could not stop the timer handler that is running and the refcount
> of sock is not managed properly.
>
> One of the UAF bugs is shown below:
>
> (thread 1) | (thread 2)
> | rose_bind
> | rose_connect
> | rose_start_heartbeat
> rose_release | (wait a time)
> case ROSE_STATE_0 |
> rose_destroy_socket | rose_heartbeat_expiry
> rose_stop_heartbeat |
> sock_put(sk) | ...
> sock_put(sk) // FREE |
> | bh_lock_sock(sk) // USE
>
> The sock is deallocated by sock_put() in rose_release() and
> then used by bh_lock_sock() in rose_heartbeat_expiry().
>
> Although rose_destroy_socket() calls rose_stop_heartbeat(),
> it could not stop the timer that is running.
>
> The KASAN report triggered by POC is shown below:
>
> BUG: KASAN: use-after-free in _raw_spin_lock+0x5a/0x110
> Write of size 4 at addr ffff88800ae59098 by task swapper/3/0
> ...
> Call Trace:
> <IRQ>
> dump_stack_lvl+0xbf/0xee
> print_address_description+0x7b/0x440
> print_report+0x101/0x230
> ? irq_work_single+0xbb/0x140
> ? _raw_spin_lock+0x5a/0x110
> kasan_report+0xed/0x120
> ? _raw_spin_lock+0x5a/0x110
> kasan_check_range+0x2bd/0x2e0
> _raw_spin_lock+0x5a/0x110
> rose_heartbeat_expiry+0x39/0x370
> ? rose_start_heartbeat+0xb0/0xb0
> call_timer_fn+0x2d/0x1c0
> ? rose_start_heartbeat+0xb0/0xb0
> expire_timers+0x1f3/0x320
> __run_timers+0x3ff/0x4d0
> run_timer_softirq+0x41/0x80
> __do_softirq+0x233/0x544
> irq_exit_rcu+0x41/0xa0
> sysvec_apic_timer_interrupt+0x8c/0xb0
> </IRQ>
> <TASK>
> asm_sysvec_apic_timer_interrupt+0x1b/0x20
> RIP: 0010:default_idle+0xb/0x10
> RSP: 0018:ffffc9000012fea0 EFLAGS: 00000202
> RAX: 000000000000bcae RBX: ffff888006660f00 RCX: 000000000000bcae
> RDX: 0000000000000001 RSI: ffffffff843a11c0 RDI: ffffffff843a1180
> RBP: dffffc0000000000 R08: dffffc0000000000 R09: ffffed100da36d46
> R10: dfffe9100da36d47 R11: ffffffff83cf0950 R12: 0000000000000000
> R13: 1ffff11000ccc1e0 R14: ffffffff8542af28 R15: dffffc0000000000
> ...
> Allocated by task 146:
> __kasan_kmalloc+0xc4/0xf0
> sk_prot_alloc+0xdd/0x1a0
> sk_alloc+0x2d/0x4e0
> rose_create+0x7b/0x330
> __sock_create+0x2dd/0x640
> __sys_socket+0xc7/0x270
> __x64_sys_socket+0x71/0x80
> do_syscall_64+0x43/0x90
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> Freed by task 152:
> kasan_set_track+0x4c/0x70
> kasan_set_free_info+0x1f/0x40
> ____kasan_slab_free+0x124/0x190
> kfree+0xd3/0x270
> __sk_destruct+0x314/0x460
> rose_release+0x2fa/0x3b0
> sock_close+0xcb/0x230
> __fput+0x2d9/0x650
> task_work_run+0xd6/0x160
> exit_to_user_mode_loop+0xc7/0xd0
> exit_to_user_mode_prepare+0x4e/0x80
> syscall_exit_to_user_mode+0x20/0x40
> do_syscall_64+0x4f/0x90
> entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
> This patch adds refcount of sock when we use functions
> such as rose_start_heartbeat() and so on to start timer,
> and decreases the refcount of sock when timer is finished
> or deleted by functions such as rose_stop_heartbeat()
> and so on. As a result, the UAF bugs could be mitigated.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> Tested-by: Duoming Zhou <duoming@....edu.cn>
> ---
> net/rose/rose_timer.c | 22 +++++++++++++---------
> 1 file changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/net/rose/rose_timer.c b/net/rose/rose_timer.c
> index b3138fc2e55..18d1912520b 100644
> --- a/net/rose/rose_timer.c
> +++ b/net/rose/rose_timer.c
> @@ -36,7 +36,7 @@ void rose_start_heartbeat(struct sock *sk)
> sk->sk_timer.function = rose_heartbeat_expiry;
> sk->sk_timer.expires = jiffies + 5 * HZ;
>
> - add_timer(&sk->sk_timer);
> + sk_reset_timer(sk, &sk->sk_timer, sk->sk_timer.expires);
> }
>
> void rose_start_t1timer(struct sock *sk)
> @@ -48,7 +48,7 @@ void rose_start_t1timer(struct sock *sk)
> rose->timer.function = rose_timer_expiry;
> rose->timer.expires = jiffies + rose->t1;
>
> - add_timer(&rose->timer);
> + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
> }
>
> void rose_start_t2timer(struct sock *sk)
> @@ -60,7 +60,7 @@ void rose_start_t2timer(struct sock *sk)
> rose->timer.function = rose_timer_expiry;
> rose->timer.expires = jiffies + rose->t2;
>
> - add_timer(&rose->timer);
> + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
> }
>
> void rose_start_t3timer(struct sock *sk)
> @@ -72,7 +72,7 @@ void rose_start_t3timer(struct sock *sk)
> rose->timer.function = rose_timer_expiry;
> rose->timer.expires = jiffies + rose->t3;
>
> - add_timer(&rose->timer);
> + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
> }
>
> void rose_start_hbtimer(struct sock *sk)
> @@ -84,7 +84,7 @@ void rose_start_hbtimer(struct sock *sk)
> rose->timer.function = rose_timer_expiry;
> rose->timer.expires = jiffies + rose->hb;
>
> - add_timer(&rose->timer);
> + sk_reset_timer(sk, &rose->timer, rose->timer.expires);
> }
>
> void rose_start_idletimer(struct sock *sk)
> @@ -97,23 +97,23 @@ void rose_start_idletimer(struct sock *sk)
> rose->idletimer.function = rose_idletimer_expiry;
> rose->idletimer.expires = jiffies + rose->idle;
>
> - add_timer(&rose->idletimer);
> + sk_reset_timer(sk, &rose->idletimer, rose->idletimer.expires);
A few lines above there is still a 'del_timer(&rose->idletimer);' call
which must be converted to sk_stop_timer(), otherwise there will be a
possible sk reference leak.
There are other del_timer(&rose->timer) that need conversion.
Thanks
Paolo
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