From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5C83911706 for ; Mon, 11 Sep 2023 14:49:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD457C433C8; Mon, 11 Sep 2023 14:49:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694443747; bh=suNk0lVzZt0fSPMhuawZe77TckFn+lkBv0b+GC2W4Xs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ybd4pMNaxjRSkLqFdnBdLmN96lRZIEVQFIBHPrEZqwNUtYM0BpPvGvwBBng56AzoQ StTH4qXLKl66MGjBa26WvFIC4QeXhRU4Po65HpOO33DXsECFtLu8wl2VRraMVCEV20 RH96X5w3pGqTrVIAcyFYB2gZlnDoOAIwD3nw/j3M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Daniel Marcovitch , Vasant Hegde , Joerg Roedel , Sasha Levin Subject: [PATCH 6.4 485/737] iommu/amd/iommu_v2: Fix pasid_state refcount dec hit 0 warning on pasid unbind Date: Mon, 11 Sep 2023 15:45:44 +0200 Message-ID: <20230911134704.125116921@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230911134650.286315610@linuxfoundation.org> References: <20230911134650.286315610@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Marcovitch [ Upstream commit 534103bcd52ca9c1fecbc70e717b4a538dc4ded8 ] When unbinding pasid - a race condition exists vs outstanding page faults. To prevent this, the pasid_state object contains a refcount. * set to 1 on pasid bind * incremented on each ppr notification start * decremented on each ppr notification done * decremented on pasid unbind Since refcount_dec assumes that refcount will never reach 0: the current implementation causes the following to be invoked on pasid unbind: REFCOUNT_WARN("decrement hit 0; leaking memory") Fix this issue by changing refcount_dec to refcount_dec_and_test to explicitly handle refcount=1. Fixes: 8bc54824da4e ("iommu/amd: Convert from atomic_t to refcount_t on pasid_state->count") Signed-off-by: Daniel Marcovitch Signed-off-by: Vasant Hegde Link: https://lore.kernel.org/r/20230609105146.7773-2-vasant.hegde@amd.com Signed-off-by: Joerg Roedel Signed-off-by: Sasha Levin --- drivers/iommu/amd/iommu_v2.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c index 261352a232716..65d78d7e04408 100644 --- a/drivers/iommu/amd/iommu_v2.c +++ b/drivers/iommu/amd/iommu_v2.c @@ -262,8 +262,8 @@ static void put_pasid_state(struct pasid_state *pasid_state) static void put_pasid_state_wait(struct pasid_state *pasid_state) { - refcount_dec(&pasid_state->count); - wait_event(pasid_state->wq, !refcount_read(&pasid_state->count)); + if (!refcount_dec_and_test(&pasid_state->count)) + wait_event(pasid_state->wq, !refcount_read(&pasid_state->count)); free_pasid_state(pasid_state); } -- 2.40.1