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Fri, 26 Jan 2024 07:29:03 -0800 (PST) Received: from dianders.sjc.corp.google.com ([2620:15c:9d:2:8218:45d8:d8fe:f7f2]) by smtp.gmail.com with ESMTPSA id a22-20020a62d416000000b006d9be279432sm1267169pfh.2.2024.01.26.07.29.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jan 2024 07:29:02 -0800 (PST) From: Douglas Anderson To: Kees Cook Cc: Douglas Anderson , Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: [PATCH] lkdtm/bugs: In lkdtm_HUNG_TASK() use BUG(), not BUG_ON(1) Date: Fri, 26 Jan 2024 07:28:53 -0800 Message-ID: <20240126072852.1.Ib065e528a8620474a72f15baa2feead1f3d89865@changeid> X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1789167361128167959 X-GMAIL-MSGID: 1789167361128167959 In commit edb6538da3df ("lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid tail call optimization") we marked lkdtm_HUNG_TASK() as __noreturn. The compiler gets unhappy if it thinks a __noreturn function might return, so there's a BUG_ON(1) at the end. Any human can see that the function won't return and the compiler can figure that out too. Except when it can't. The MIPS architecture defines HAVE_ARCH_BUG_ON and defines its own version of BUG_ON(). The MIPS version of BUG_ON() is not a macro but is instead an inline function. Apparently this prevents the compiler from realizing that the condition to BUG_ON() is constant and that the function will never return. Let's change the BUG_ON(1) to just BUG(), which it should have been to begin with. The only reason I used BUG_ON(1) to begin with was because I was used to using WARN_ON(1) when writing test code and WARN() and BUG() are oddly inconsistent in this manner. :-/ Fixes: edb6538da3df ("lkdtm/bugs: Adjust lkdtm_HUNG_TASK() to avoid tail call optimization") Signed-off-by: Douglas Anderson --- drivers/misc/lkdtm/bugs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index d1222d3eda2f..b92767d6bdd2 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -298,7 +298,7 @@ static void __noreturn lkdtm_HUNG_TASK(void) { set_current_state(TASK_UNINTERRUPTIBLE); schedule(); - BUG_ON(1); + BUG(); } static volatile unsigned int huge = INT_MAX - 2;