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authorNadav Amit <namit@vmware.com>2019-04-26 02:11:41 +0200
committerIngo Molnar <mingo@kernel.org>2019-04-30 12:38:01 +0200
commit3950746d9d8ef981c1cb842384e0e86e8d1aad76 (patch)
tree1e19dfe4c84a6196653a246e22d63cdd9628ef4a
parentx86/kprobes: Use vmalloc special flag (diff)
downloadlinux-3950746d9d8ef981c1cb842384e0e86e8d1aad76.tar.xz
linux-3950746d9d8ef981c1cb842384e0e86e8d1aad76.zip
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@vmware.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <akpm@linux-foundation.org> Cc: <ard.biesheuvel@linaro.org> Cc: <deneen.t.dock@intel.com> Cc: <kernel-hardening@lists.openwall.com> Cc: <kristen@linux.intel.com> Cc: <linux_dti@icloud.com> Cc: <will.deacon@arm.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190426001143.4983-22-namit@vmware.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--arch/x86/kernel/alternative.c5
1 files changed, 5 insertions, 0 deletions
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)
{