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Wed, 11 Nov 2026 07:50:03 -0800 (PST) Received: from pathway.suse.cz ([176.114.240.130]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-498369a3fd2sm12466493f8f.52.2026.11.11.07.50.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 07:50:02 -0800 (PST) From: Petr Mladek To: John Ogness Cc: Sergey Senozhatsky , Steven Rostedt , Marcos Paulo de Souza , Chris Down , Naveen Kumar Chaudhary , printk@lists.linux.dev, linux-kernel@vger.kernel.org, Petr Mladek Subject: [PATCH v7 08/17] printk: Ensure consistent name and devname when updating preferred console Date: Wed, 11 Nov 2026 16:48:07 +0100 Message-ID: <20261111154816.71103-9-pmladek@suse.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261111154816.71103-1-pmladek@suse.com> References: <20261111154816.71103-1-pmladek@suse.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Make sure that add_or_update_preferred_console() updates the right entry. The current caller does the right thing. The new paranoid checks prevent a potential misuse of the API in the future. Signed-off-by: Petr Mladek --- kernel/printk/printk.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index a76f37c1b431..e9b189eae548 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2564,6 +2564,8 @@ asmlinkage __visible void early_printk(const char *fmt, ...) * * 2. Either @name and valid @idx OR @devname and @idx=-1 are allowed. [*] * + * 3. Only matching entries can be updated. + * * [*] A valid @name and @idx will get assigned for a devname later when * @devname matches during the device initialization, see * match_devname_and_update_preferred_console(). @@ -2623,6 +2625,19 @@ static int add_or_update_preferred_console(unsigned int i, } pc->index = idx; + } else { + /* Make sure that only matching entries are updated. */ + if (name && (strcmp(pc->name, name) || (pc->index != idx))) { + pr_err("Updating a preferred console with an invalid name or index: %s%d vs. %s%d\n", + pc->name, pc->index, name, idx); + return -EINVAL; + } + + if (devname && strcmp(pc->devname, devname)) { + pr_err("Updating a preferred console with an invalid devname: %s vs. %s\n", + pc->devname, devname); + return -EINVAL; + } } /* -- 2.56.0