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Wed, 29 May 2024 06:36:29 -0700 (PDT) Received: from [192.168.50.95] ([118.32.98.101]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1f5e6a0c323sm7448965ad.259.2024.05.29.06.36.26 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 May 2024 06:36:28 -0700 (PDT) Message-ID: <12ac8cc2-3117-4cb5-ab3a-2e8add3270a6@gmail.com> Date: Wed, 29 May 2024 22:36:24 +0900 Precedence: bulk X-Mailing-List: linux-kernel-mentees@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] xen/xenbus: handle potential dangling pointer issue in xen_pcibk_xenbus_probe To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , Stefano Stabellini , Oleksandr Tyshchenko Cc: skhan@linuxfoundation.org, sj@kernel.org, Austin Kim , shjy180909@gmail.com, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-kernel-mentees@lists.linuxfoundation.org References: <20240529122232.25360-1-yskelg@gmail.com> <0c53415d-3394-455a-a6b5-99d3efb92318@suse.com> Content-Language: en-US From: Yunseong Kim In-Reply-To: <0c53415d-3394-455a-a6b5-99d3efb92318@suse.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 5/29/24 9:27 오후, Jürgen Groß wrote: > On 29.05.24 14:22, yskelg@gmail.com wrote: >> From: Yunseong Kim >> >> If 'xen_pcibk_init_devices()' fails. This ensures that 'pdev->xdev' does >> not point to 'xdev' when 'pdev' is freed. >> >> Signed-off-by: Yunseong Kim >> --- >>   drivers/xen/xen-pciback/xenbus.c | 1 + >>   1 file changed, 1 insertion(+) >> >> diff --git a/drivers/xen/xen-pciback/xenbus.c >> b/drivers/xen/xen-pciback/xenbus.c >> index b11e401f1b1e..348d6803b8c0 100644 >> --- a/drivers/xen/xen-pciback/xenbus.c >> +++ b/drivers/xen/xen-pciback/xenbus.c >> @@ -54,6 +54,7 @@ static struct xen_pcibk_device *alloc_pdev(struct >> xenbus_device *xdev) >>       INIT_WORK(&pdev->op_work, xen_pcibk_do_op); >>         if (xen_pcibk_init_devices(pdev)) { >> +        pdev->xdev = NULL; >>           kfree(pdev); >>           pdev = NULL; >>       } > > NAK. > > This doesn't make any sense, as pdev is freed. > > > Juergen Thanks for the code review Juergen! I don't know if it's a big deal, but I think that if pdev->xdev don't replace it with NULL, 'struct xenbus_device *xdev' address value stays in the kmalloc cached memory. And most of the kernel code I've seen does this (even when it's 'free_pdev()'), so I sent a patch. In the very unlikely event that. I was thinking if someone look at the value without initializing the kmalloced memory, someone might see the 'xenbus_device *xdev address'. Warm Regards, Yunseong Kim