[PATCH v2 20/20] x86/alternative: comment about module removal races
From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: 2019-01-29 00:39:34
Also in:
linux-integrity, linux-mm, lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
From: Nadav Amit <redacted> 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 <redacted> 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 81876e3ef3fd..cc3b6222857a 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c@@ -807,6 +807,11 @@ 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