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SubjectRe: Nokia N900: refcount_t underflow, use after free
Date
Hi Pavel,

On 03/08/2018 10:59 AM, Tony Lindgren wrote:
> * Pavel Machek <pavel@ucw.cz> [180308 14:31]:
>> Hi!
>>
>> I'm getting this warning... Has anyone seen/debugged that before?
>> Unfortunately the backtrace does not seem to be too useful :-(.
>
> Adding Suman to Cc, as it points to arm_iommu_release_mapping().

Hmm, we need to find out if the failure paths in isp_probe() are
mismatched, or if this is coming from some mismatch between the OMAP
IOMMU driver and the DMA plumbing. AFAIK, the cleanup paths in this
driver hasn't changed in sometime. Do you see this on mainline branch or
just the next branch? Also, can you check where you are failing in the
isp_probe and if the warning is seen before or after the function
returns. I don't have any OMAP3 board nor any ISP-enabled device to
check this behavior.

regards
Suman

>
> Regards,
>
> Tony
>
>> [ 0.000000] Booting Linux on physical CPU 0x0
>> [ 0.000000] Linux version 4.16.0-rc3-next-20180302 (pavel@duo) (gcc
>> version 4.7.2 (GC
>> C)) #70 Fri Mar 2 10:16:00 CET 2018
>> [ 0.000000] CPU: ARMv7 Processor [411fc083] revision 3 (ARMv7),
>> cr=10c5387d
>> [ 0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT
>> nonaliasing instruction cac
>> ...
>> [ 1.244140] omap3isp 480bc000.isp: 480bc000.isp supply vdd-csiphy2
>> not found, using d
>> ummy regulator
>> [ 1.254089] omap3isp 480bc000.isp: Revision 2.0 found
>> [ 1.260009] omap-iommu 480bd400.mmu: 480bd400.mmu: version 1.1
>> [ 1.266693] ------------[ cut here ]------------
>> [ 1.271606] WARNING: CPU: 0 PID: 1 at lib/refcount.c:187
>> refcount_sub_and_test+0x94/0xa8
>> [ 1.280181] refcount_t: underflow; use-after-free.
>> [ 1.285247] Modules linked in:
>> [ 1.288482] CPU: 0 PID: 1 Comm: swapper Not tainted
>> 4.16.0-rc3-next-20180302 #70
>> [ 1.296295] Hardware name: Nokia RX-51 board
>> [ 1.300811] [<c010d6cc>] (unwind_backtrace) from [<c010b560>]
>> (show_stack+0x10/0x14)
>> [ 1.309020] [<c010b560>] (show_stack) from [<c0127dec>]
>> (__warn+0xe8/0x110)
>> [ 1.316375] [<c0127dec>] (__warn) from [<c0127edc>]
>> (warn_slowpath_fmt+0x38/0x48)
>> [ 1.324310] [<c0127edc>] (warn_slowpath_fmt) from [<c034e630>]
>> (refcount_sub_and_test+0x94/0xa8)
>> [ 1.333557] [<c034e630>] (refcount_sub_and_test) from [<c01109a8>]
>> (arm_iommu_release_mapping+0x18/0x2c)
>> [ 1.343597] [<c01109a8>] (arm_iommu_release_mapping) from
>> [<c041752c>] (driver_probe_device+0x24c/0x314)
>> [ 1.353637] [<c041752c>] (driver_probe_device) from [<c04176a0>]
>> (__driver_attach+0xac/0xb0)
>> [ 1.362548] [<c04176a0>] (__driver_attach) from [<c0415b94>]
>> (bus_for_each_dev+0x58/0x7c)
>> [ 1.371185] [<c0415b94>] (bus_for_each_dev) from [<c0416a14>]
>> (bus_add_driver+0xe0/0x1f0)
>> [ 1.379852] [<c0416a14>] (bus_add_driver) from [<c0417f10>]
>> (driver_register+0x78/0xf4)
>> [ 1.388305] [<c0417f10>] (driver_register) from [<c010257c>]
>> (do_one_initcall+0x3c/0x16c)
>> [ 1.396972] [<c010257c>] (do_one_initcall) from [<c0b00d5c>]
>> (kernel_init_freeable+0xf8/0x1c4)
>> [ 1.406066] [<c0b00d5c>] (kernel_init_freeable) from [<c071640c>]
>> (kernel_init+0x8/0x108)
>> [ 1.414703] [<c071640c>] (kernel_init) from [<c01010e8>]
>> (ret_from_fork+0x14/0x2c)
>> [ 1.422698] Exception stack(0xce049fb0 to 0xce049ff8)
>> [ 1.428039] 9fa0: 00000000
>> 00000000 00000000 00000000
>> [ 1.436676] 9fc0: 00000000 00000000 00000000 00000000 00000000
>> 00000000 00000000 00000000
>> [ 1.445312] 9fe0: 00000000 00000000 00000000 00000000 00000013
>> 00000000
>> [ 1.452270] ---[ end trace dcb3a72772bbfe7a ]---
>> [ 1.459045] ti-soc-thermal 48002524.bandgap: This OMAP thermal
>> sensor is unreliable. You've been warned
>> [ 1.469055] ti-soc-thermal 48002524.bandgap: Non-trimmed BGAP, Temp
>> not accurate
>> [ 1.476898] ti-soc-thermal 48002524.bandgap: thermal zone device is
>> NULL
>> [ 1.485198] omap_wdt: OMAP Watchdog Timer Rev 0x31: initial timeout
>> 60 sec
>> [ 1.495208] omap_hsmmc 4809c000.mmc: GPIO lookup for consumer cd
>>
>> --
>> (english) http://www.livejournal.com/~pavelmachek
>> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
>
>

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