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From:   Nadav Amit <namit@vmware.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
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        Rick Edgecombe <rick.p.edgecombe@intel.com>,
        Nadav Amit <namit@vmware.com>,
        Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCH v5 21/23] x86/alternative: Comment about module removal races
Date:   Thu, 25 Apr 2019 17:11:41 -0700
Message-ID: <20190426001143.4983-22-namit@vmware.com>
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Add a comment to clarify that users of text_poke() must ensure that
no races with module removal take place.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Nadav Amit <namit@vmware.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
 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)
 {
-- 
2.17.1