From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 30 Apr 2019 04:29:34 -0700 Sender: tip tree robot From: tip-bot for Nadav Amit Message-ID: In-Reply-To: <20190426001143.4983-22-namit@vmware.com> References: <20190426001143.4983-22-namit@vmware.com> Subject: [tip:x86/mm] x86/alternatives: Add comment about module removal races MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline To: linux-tip-commits@vger.kernel.org Cc: ard.biesheuvel@linaro.org, bp@alien8.de, dave.hansen@linux.intel.com, linux_dti@icloud.com, riel@surriel.com, akpm@linux-foundation.org, deneen.t.dock@intel.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, kristen@linux.intel.com, hpa@zytor.com, will.deacon@arm.com, mingo@kernel.org, mhiramat@kernel.org, tglx@linutronix.de, rick.p.edgecombe@intel.com, luto@kernel.org, kernel-hardening@lists.openwall.com, peterz@infradead.org, namit@vmware.com List-ID: Commit-ID: 3950746d9d8ef981c1cb842384e0e86e8d1aad76 Gitweb: https://git.kernel.org/tip/3950746d9d8ef981c1cb842384e0e86e8d1aad76 Author: Nadav Amit AuthorDate: Thu, 25 Apr 2019 17:11:41 -0700 Committer: Ingo Molnar CommitDate: Tue, 30 Apr 2019 12:38:01 +0200 x86/alternatives: Add comment about module removal races Add a comment to clarify that users of text_poke() must ensure that no races with module removal take place. Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Cc: Cc: Cc: Cc: Cc: Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Rik van Riel Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190426001143.4983-22-namit@vmware.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/alternative.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 18f959975ea0..7b9b49dfc05a 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -810,6 +810,11 @@ static void *__text_poke(void *addr, const void *opcode, size_t len) * It means the size must be writable atomically and the address must be aligned * in a way that permits an atomic write. It also makes sure we fit on a single * page. + * + * Note that the caller must ensure that if the modified code is part of a + * module, the module would not be removed during poking. This can be achieved + * by registering a module notifier, and ordering module removal and patching + * trough a mutex. */ void *text_poke(void *addr, const void *opcode, size_t len) {