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Message-ID: <tip-3950746d9d8ef981c1cb842384e0e86e8d1aad76@git.kernel.org>
Date: Tue, 30 Apr 2019 04:29:34 -0700
From: tip-bot for Nadav Amit <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: ard.biesheuvel@...aro.org, bp@...en8.de, dave.hansen@...ux.intel.com,
linux_dti@...oud.com, riel@...riel.com, akpm@...ux-foundation.org,
deneen.t.dock@...el.com, linux-kernel@...r.kernel.org,
torvalds@...ux-foundation.org, kristen@...ux.intel.com, hpa@...or.com,
will.deacon@....com, mingo@...nel.org, mhiramat@...nel.org,
tglx@...utronix.de, rick.p.edgecombe@...el.com, luto@...nel.org,
kernel-hardening@...ts.openwall.com, peterz@...radead.org,
namit@...are.com
Subject: [tip:x86/mm] x86/alternatives: Add comment about module removal
races
Commit-ID: 3950746d9d8ef981c1cb842384e0e86e8d1aad76
Gitweb: https://git.kernel.org/tip/3950746d9d8ef981c1cb842384e0e86e8d1aad76
Author: Nadav Amit <namit@...are.com>
AuthorDate: Thu, 25 Apr 2019 17:11:41 -0700
Committer: Ingo Molnar <mingo@...nel.org>
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 <namit@...are.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: <akpm@...ux-foundation.org>
Cc: <ard.biesheuvel@...aro.org>
Cc: <deneen.t.dock@...el.com>
Cc: <kernel-hardening@...ts.openwall.com>
Cc: <kristen@...ux.intel.com>
Cc: <linux_dti@...oud.com>
Cc: <will.deacon@....com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Rik van Riel <riel@...riel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/20190426001143.4983-22-namit@vmware.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
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)
{
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