linux-kernel - Re: [PATCH] Revert "media: dvb-core: Fix use-after-free on race condition at dvb

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Date:   Fri, 16 Jun 2023 08:46:20 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "media: dvb-core: Fix use-after-free on race condition at dvb_frontend"

On Fri, 09 Jun 2023 10:22:38 +0200,
Mauro Carvalho Chehab wrote:
> 
> As reported by Thomas Voegtle <tv@...96.de>, sometimes a DVB card does
> not initialize properly booting Linux 6.4-rc4. This is not always, maybe
> in 3 out of 4 attempts.
> 
> After double-checking, the root cause seems to be related to the
> UAF fix, which is causing a race issue:
> 
> [   26.332149] tda10071 7-0005: found a 'NXP TDA10071' in cold state, will try to load a firmware
> [   26.340779] tda10071 7-0005: downloading firmware from file 'dvb-fe-tda10071.fw'
> [  989.277402] INFO: task vdr:743 blocked for more than 491 seconds.
> [  989.283504]       Not tainted 6.4.0-rc5-i5 #249
> [  989.288036] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> [  989.295860] task:vdr             state:D stack:0     pid:743   ppid:711    flags:0x00004002
> [  989.295865] Call Trace:
> [  989.295867]  <TASK>
> [  989.295869]  __schedule+0x2ea/0x12d0
> [  989.295877]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
> [  989.295881]  schedule+0x57/0xc0
> [  989.295884]  schedule_preempt_disabled+0xc/0x20
> [  989.295887]  __mutex_lock.isra.16+0x237/0x480
> [  989.295891]  ? dvb_get_property.isra.10+0x1bc/0xa50
> [  989.295898]  ? dvb_frontend_stop+0x36/0x180
> [  989.338777]  dvb_frontend_stop+0x36/0x180
> [  989.338781]  dvb_frontend_open+0x2f1/0x470
> [  989.338784]  dvb_device_open+0x81/0xf0
> [  989.338804]  ? exact_lock+0x20/0x20
> [  989.338808]  chrdev_open+0x7f/0x1c0
> [  989.338811]  ? generic_permission+0x1a2/0x230
> [  989.338813]  ? link_path_walk.part.63+0x340/0x380
> [  989.338815]  ? exact_lock+0x20/0x20
> [  989.338817]  do_dentry_open+0x18e/0x450
> [  989.374030]  path_openat+0xca5/0xe00
> [  989.374031]  ? terminate_walk+0xec/0x100
> [  989.374034]  ? path_lookupat+0x93/0x140
> [  989.374036]  do_filp_open+0xc0/0x140
> [  989.374038]  ? __call_rcu_common.constprop.91+0x92/0x240
> [  989.374041]  ? __check_object_size+0x147/0x260
> [  989.374043]  ? __check_object_size+0x147/0x260
> [  989.374045]  ? alloc_fd+0xbb/0x180
> [  989.374048]  ? do_sys_openat2+0x243/0x310
> [  989.374050]  do_sys_openat2+0x243/0x310
> [  989.374052]  do_sys_open+0x52/0x80
> [  989.374055]  do_syscall_64+0x5b/0x80
> [  989.421335]  ? __task_pid_nr_ns+0x92/0xa0
> [  989.421337]  ? syscall_exit_to_user_mode+0x20/0x40
> [  989.421339]  ? do_syscall_64+0x67/0x80
> [  989.421341]  ? syscall_exit_to_user_mode+0x20/0x40
> [  989.421343]  ? do_syscall_64+0x67/0x80
> [  989.421345]  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [  989.421348] RIP: 0033:0x7fe895d067e3
> [  989.421349] RSP: 002b:00007fff933c2ba0 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
> [  989.421351] RAX: ffffffffffffffda RBX: 00007fff933c2c10 RCX: 00007fe895d067e3
> [  989.421352] RDX: 0000000000000802 RSI: 00005594acdce160 RDI: 00000000ffffff9c
> [  989.421353] RBP: 0000000000000802 R08: 0000000000000000 R09: 0000000000000000
> [  989.421353] R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
> [  989.421354] R13: 00007fff933c2ca0 R14: 00000000ffffffff R15: 00007fff933c2c90
> [  989.421355]  </TASK>
> 
> This reverts commit 6769a0b7ee0c3b31e1b22c3fadff2bfb642de23f.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>

Note that CVE-2022-45885 was assigned for the original issue as a
security bug, and now it's reopened by this revert.

Please let me know if you have a fix in another form.


thanks,

Takashi