Messages in this thread |  | | Date | Mon, 4 Apr 2022 00:45:04 +0700 | Subject | Re: [PATCH v6 2/2] x86/MCE/AMD: Fix memory leak when `threshold_create_bank()` fails | From | Ammar Faizi <> |
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On 4/4/22 12:43 AM, Ammar Faizi wrote: > 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.
(only if it's really safe)
-- Ammar Faizi
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