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[75.142.250.213]) by smtp.gmail.com with ESMTPSA id l3sm3832360qtn.69.2020.07.09.08.31.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Jul 2020 08:31:30 -0700 (PDT) From: trix@redhat.com To: stuyoder@gmail.com, laurentiu.tudor@nxp.com, gregkh@linuxfoundation.org Cc: linux-kernel@vger.kernel.org, Tom Rix Subject: [PATCH v3] bus: fsl-mc: fix invalid free in fsl_mc_device_add Date: Thu, 9 Jul 2020 08:31:19 -0700 Message-Id: <20200709153119.5051-1-trix@redhat.com> X-Mailer: git-send-email 2.18.1 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tom Rix clang static analysis flags this error fsl-mc-bus.c:695:2: warning: Attempt to free released memory [unix.Malloc] kfree(mc_dev); ^~~~~~~~~~~~~ The problem block of code is mc_bus = kzalloc(sizeof(*mc_bus), GFP_KERNEL); if (!mc_bus) return -ENOMEM; mc_dev = &mc_bus->mc_dev; mc_bus's structure contains a mc_dev element, freeing it later is not appropriate. So check if mc_bus was allocated before freeing mc_dev This is a case where checkpatch WARNING: kfree(NULL) is safe and this check is probably not required + if (mc_bus) + kfree(mc_bus); is wrong. Fixes: a042fbed0290 ("staging: fsl-mc: simplify couple of deallocations") Signed-off-by: Tom Rix --- v1: add a comment to explain freeing uniqueness v2: add gregkh's suggestion to comment. drivers/bus/fsl-mc/fsl-mc-bus.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c index 40526da5c6a6..839d96d03f0d 100644 --- a/drivers/bus/fsl-mc/fsl-mc-bus.c +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c @@ -691,8 +691,16 @@ int fsl_mc_device_add(struct fsl_mc_obj_desc *obj_desc, error_cleanup_dev: kfree(mc_dev->regions); - kfree(mc_bus); - kfree(mc_dev); + /* + * mc_bus allocates a private version of mc_dev + * it is not appropriate to free the private version. + * Which means we have to check the pointer before freeing it. + * Do not remove this check. + */ + if (mc_bus) + kfree(mc_bus); + else + kfree(mc_dev); return error; } -- 2.18.1