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[119.74.6.224]) by smtp.gmail.com with ESMTPSA id af79cd13be357-93749d91ca3sm493416285a.28.2026.08.24.05.38.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 05:38:28 -0700 (PDT) From: Wei Jie Law <98lawweijie@gmail.com> To: Dmitry Torokhov Cc: Andrew Duggan , Jiri Kosina , Benjamin Tissoires , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] Input: synaptics-rmi4 - reject a PDT that grows between scans Date: Mon, 24 Aug 2026 20:38:24 +0800 Message-ID: <20260824123824.78628-1-98lawweijie@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2c26d7ce8c6b7371ab55607f53443961220e4b24.1787549234.git.98lawweijie@gmail.com> References: <2c26d7ce8c6b7371ab55607f53443961220e4b24.1787549234.git.98lawweijie@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Superseded by v2 2/2: https://lore.kernel.org/linux-input/20260824122733.76321-3-98lawweijie@gmail.com/ Please do not apply this version. The rejection path it adds calls put_device(&fn->dev) before rmi_register_function(), which is where device_initialize() happens, so fn->dev is still all zeroes at that point. kobject_put() then warns that the kobject was never initialised, refcount_dec_and_test() warns about the underflow, and because the saturated refcount makes kref_put() return false the release never runs -- so the function is leaked on every rejection, i.e. on exactly the malicious device this patch is meant to reject: rmi4_physical rmi4-00: F40: interrupt count changed between PDT scans (pos 1 + 6 > 1) kobject: '(null)' (00000000cfabc269): is not initialized, yet kobject_put() is being called. WARNING: CPU: 0 PID: 9 at lib/kobject.c:734 kobject_put+0x1cf/0x4b0 refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 9 at lib/refcount.c:28 refcount_warn_saturate+0xf2/0x150 v2 uses kfree() instead. Please mark this one superseded. Thanks, Wei Jie