Messages in this thread | | | Date | Mon, 4 Apr 2022 00:43:47 +0700 | From | Ammar Faizi <> | Subject | Re: [PATCH v6 2/2] x86/MCE/AMD: Fix memory leak when `threshold_create_bank()` fails |
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On 4/4/22 12:03 AM, Thomas Gleixner wrote: > On Tue, Mar 29 2022 at 17:47, Ammar Faizi wrote: > >> In mce_threshold_create_device(), if threshold_create_bank() fails, the >> @bp will be leaked, because the call to mce_threshold_remove_device() >> will not free the @bp. mce_threshold_remove_device() frees >> @threshold_banks. At that point, the @bp has not been written to >> @threshold_banks, @threshold_banks is NULL, so the call is just a nop. >> >> Fix this by extracting the cleanup part into a new static function >> __threshold_remove_device(), then call it from create/remove device >> functions. > > The way simpler fix is to move > >> } >> this_cpu_write(threshold_banks, bp); > > before the loop. That's safe because the banks cannot yet be reached via > an MCE as the vector is not yet enabled: > >> if (thresholding_irq_en) >> mce_threshold_vector = amd_threshold_interrupt; Thomas,
I did like what you said (in the patch v4), but after Yazen and Borislav reviewed it, we got a conclusion that it's not safe.
See [1] and [2] for the full message.
[1]: https://lore.kernel.org/lkml/YkFsQhpGGXIFTMyp@zn.tnic/ [2]: https://lore.kernel.org/lkml/Yh+oyD%2F5M3TW5ZMM@yaz-ubuntu/
Yazen, Borislav, please take a deeper look on this again. I will send a v7 revision to really make it simpler by moving that "per-CPU var write" before the loop.
Thanks!
-- Ammar Faizi
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