Re: [PATCH v2 5.15] tty: n_gsm: Fix use-after-free in gsm_cleanup_mux

["Yu, Mingli" <mingli.yu@windriver.com>]

Hi Greg,

Sorry for confusion!

Please use v2 instead as we correct the author in v2.

Thanks,
Mingli

On 12/2/24 17:36, Greg KH wrote:
> CAUTION: This email comes from a non Wind River email account!
> Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> On Thu, Nov 28, 2024 at 04:47:30PM +0800, mingli.yu@eng.windriver.com wrote:
>> From: Longlong Xia <xialonglong@kylinos.cn>
>>
>> commit 9462f4ca56e7d2430fdb6dcc8498244acbfc4489 upstream.
>>
>> BUG: KASAN: slab-use-after-free in gsm_cleanup_mux+0x77b/0x7b0
>> drivers/tty/n_gsm.c:3160 [n_gsm]
>> Read of size 8 at addr ffff88815fe99c00 by task poc/3379
>> CPU: 0 UID: 0 PID: 3379 Comm: poc Not tainted 6.11.0+ #56
>> Hardware name: VMware, Inc. VMware Virtual Platform/440BX
>> Desktop Reference Platform, BIOS 6.00 11/12/2020
>> Call Trace:
>>   <TASK>
>>   gsm_cleanup_mux+0x77b/0x7b0 drivers/tty/n_gsm.c:3160 [n_gsm]
>>   __pfx_gsm_cleanup_mux+0x10/0x10 drivers/tty/n_gsm.c:3124 [n_gsm]
>>   __pfx_sched_clock_cpu+0x10/0x10 kernel/sched/clock.c:389
>>   update_load_avg+0x1c1/0x27b0 kernel/sched/fair.c:4500
>>   __pfx_min_vruntime_cb_rotate+0x10/0x10 kernel/sched/fair.c:846
>>   __rb_insert_augmented+0x492/0xbf0 lib/rbtree.c:161
>>   gsmld_ioctl+0x395/0x1450 drivers/tty/n_gsm.c:3408 [n_gsm]
>>   _raw_spin_lock_irqsave+0x92/0xf0 arch/x86/include/asm/atomic.h:107
>>   __pfx_gsmld_ioctl+0x10/0x10 drivers/tty/n_gsm.c:3822 [n_gsm]
>>   ktime_get+0x5e/0x140 kernel/time/timekeeping.c:195
>>   ldsem_down_read+0x94/0x4e0 arch/x86/include/asm/atomic64_64.h:79
>>   __pfx_ldsem_down_read+0x10/0x10 drivers/tty/tty_ldsem.c:338
>>   __pfx_do_vfs_ioctl+0x10/0x10 fs/ioctl.c:805
>>   tty_ioctl+0x643/0x1100 drivers/tty/tty_io.c:2818
>>
>> Allocated by task 65:
>>   gsm_data_alloc.constprop.0+0x27/0x190 drivers/tty/n_gsm.c:926 [n_gsm]
>>   gsm_send+0x2c/0x580 drivers/tty/n_gsm.c:819 [n_gsm]
>>   gsm1_receive+0x547/0xad0 drivers/tty/n_gsm.c:3038 [n_gsm]
>>   gsmld_receive_buf+0x176/0x280 drivers/tty/n_gsm.c:3609 [n_gsm]
>>   tty_ldisc_receive_buf+0x101/0x1e0 drivers/tty/tty_buffer.c:391
>>   tty_port_default_receive_buf+0x61/0xa0 drivers/tty/tty_port.c:39
>>   flush_to_ldisc+0x1b0/0x750 drivers/tty/tty_buffer.c:445
>>   process_scheduled_works+0x2b0/0x10d0 kernel/workqueue.c:3229
>>   worker_thread+0x3dc/0x950 kernel/workqueue.c:3391
>>   kthread+0x2a3/0x370 kernel/kthread.c:389
>>   ret_from_fork+0x2d/0x70 arch/x86/kernel/process.c:147
>>   ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:257
>>
>> Freed by task 3367:
>>   kfree+0x126/0x420 mm/slub.c:4580
>>   gsm_cleanup_mux+0x36c/0x7b0 drivers/tty/n_gsm.c:3160 [n_gsm]
>>   gsmld_ioctl+0x395/0x1450 drivers/tty/n_gsm.c:3408 [n_gsm]
>>   tty_ioctl+0x643/0x1100 drivers/tty/tty_io.c:2818
>>
>> [Analysis]
>> gsm_msg on the tx_ctrl_list or tx_data_list of gsm_mux
>> can be freed by multi threads through ioctl,which leads
>> to the occurrence of uaf. Protect it by gsm tx lock.
>>
>> Signed-off-by: Longlong Xia <xialonglong@kylinos.cn>
>> Cc: stable <stable@kernel.org>
>> Suggested-by: Jiri Slaby <jirislaby@kernel.org>
>> Link: https://lore.kernel.org/r/20240926130213.531959-1-xialonglong@kylinos.cn
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> [Mingli: Backport to fix CVE-2024-50073, no guard macro defined resolution]
>> Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
>> ---
>>   drivers/tty/n_gsm.c | 4 ++++
>>   1 file changed, 4 insertions(+)
> 
> What differed from v1?
> 
> Please submit a v3 that says what has changed here.
> 
> thanks,
> 
> greg k-h