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[1.164.89.44]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2db14841eaasm55744225ad.8.2026.09.08.02.58.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Sep 2026 02:58:07 -0700 (PDT) Date: Tue, 8 Sep 2026 17:58:02 +0800 From: Richard Lyu To: peterhuewe@gmx.de, jarkko@kernel.org Cc: jgg@ziepe.ca, fourier.thomas@gmail.com, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, Richard Lyu Subject: [PATCH] tpm: Remove ineffective wmb() from tpm_pm_resume() Message-ID: <20260908095748.78967-1-richard.lyu@suse.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mailer: git-send-email 2.51.0 User-Agent: Mutt/2.2.16 (2025-11-22) The comment above the wmb() in tpm_pm_resume() states that the barrier guarantees TPM_CHIP_FLAG_SUSPENDED is written last, so that hwrng does not activate before the chip has been fully resumed. It cannot do so: it is placed after the store that clears the flag, and therefore does not order the preceding resume work before that store. It also has nothing to pair with, as tpm_try_get_ops() contains no matching read barrier. Drop the barrier along with the comment rather than leave a no-op behind. Should such ordering turn out to be needed, it would require paired barriers or locking. Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume") Link: https://lore.kernel.org/all/a62fc816-259a-4d28-a265-e425bc17ed50@gmail.com/ Signed-off-by: Richard Lyu --- drivers/char/tpm/tpm-interface.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index b4e749e70b02..0bab78c8767c 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -497,12 +497,6 @@ int tpm_pm_resume(struct device *dev) chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED; - /* - * Guarantee that SUSPENDED is written last, so that hwrng does not - * activate before the chip has been fully resumed. - */ - wmb(); - return 0; } EXPORT_SYMBOL_GPL(tpm_pm_resume); -- 2.51.0