Re: Free after use in fw_pm_notify()->kill_requests_without_uevent() due pending_fw_head

[Greg KH]

On Tue, Jan 03, 2017 at 06:44:03AM -0800, Sodagudi Prasad wrote:
> 
> Hi All,
> 
> Device has crashed due to memory access after free while pending_fw_head
> list accessed. Kernel 4.4 stable version is used to reproduce this use after
> free.
> ------------------------------------------------------------------------------------------
> [ 9031.178428] Unable to handle kernel paging request at virtual address
> 6b6b6b6b6b6b6b6b
> [ 9031.178508] pgd = ffffffc0de9d2000
> [ 9031.185888] [6b6b6b6b6b6b6b6b] *pgd=0000000000000000,
> *pud=0000000000000000
> [ 9031.253045] ------------[ cut here ]------------
> [ 9031.253100] Kernel BUG at ffffff800864c0a0 [verbose debug info
> unavailable]
> [ 9031.256860] Internal error: Oops - BUG: 96000004 [#1] PREEMPT SMP
> [ 9031.263539] Modules linked in:
> [ 9031.272708] CPU: 6 PID: 1373 Comm: system_server Tainted: G        W    L
> 4.4.16+ #1
> [ 9031.280648] task: ffffffc0d1a1d700 ti: ffffffc0d1a2c000 task.ti:
> ffffffc0d1a2c000
> [ 9031.287776] PC is at fw_pm_notify+0x84/0x19c
> [ 9031.295215] LR is at fw_pm_notify+0x60/0x19c
> [ 9031.511559] [] fw_pm_notify+0x84/0x19c
> [ 9031.519355] [] notifier_call_chain+0x58/0x8c
> [ 9031.524739] [] __blocking_notifier_call_chain+0x54/0x70
> [ 9031.530387] [] blocking_notifier_call_chain+0x38/0x44
> [ 9031.537243] [] pm_notifier_call_chain+0x28/0x48
> [ 9031.543662] [] pm_suspend+0x278/0x674
> [ 9031.549906] [] state_store+0x58/0x90
> [ 9031.554942] [] kobj_attr_store+0x18/0x28
> [ 9031.560154] [] sysfs_kf_write+0x5c/0x68
> [ 9031.565620] [] kernfs_fop_write+0x114/0x16c
> [ 9031.571092] [] __vfs_write+0x48/0xf0
> [ 9031.576816] [] vfs_write+0xb8/0x150
> [ 9031.581848] [] SyS_write+0x58/0x94
> [ 9031.586973] [] el0_svc_naked+0x24/0x28
> -----------------------------------------------------------------------------------------------
> 
> Kernel panic is observed during device suspend/resume path in the
> kill_requests_without_uevent() called from fw_pm_notify().
> when pending_list of a firmware_buf is accessed 0x6b(free pattern) pattern
> observed. Based on this firmware_buf is freed even if firmware_buf is part
> of
> pending_fw_head list.

What are you doing in userspace to trigger this problem?  What kernel
driver is this happening with?

And 4.4.16 is pretty old, can you try 4.9?

thanks,

greg k-h