[tip:x86/urgent] x86/alternatives: Lockdep-enforce text_mutex in text_poke*()

[tip-bot for Jiri Kosina]

Commit-ID:  9222f606506c5f8ca2c8b8c939d59ed3e6ac4148
Gitweb:     https://git.kernel.org/tip/9222f606506c5f8ca2c8b8c939d59ed3e6ac4148
Author:     Jiri Kosina <jkosina@xxxxxxx>
AuthorDate: Tue, 28 Aug 2018 08:55:14 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 30 Aug 2018 13:02:30 +0200

x86/alternatives: Lockdep-enforce text_mutex in text_poke*()

text_poke() and text_poke_bp() must be called with text_mutex held.

Put proper lockdep anotation in place instead of just mentioning the
requirement in a comment.

Reported-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Jiri Kosina <jkosina@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/nycvar.YFH.7.76.1808280853520.25787@xxxxxxxxxxxxx

---
 arch/x86/kernel/alternative.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 014f214da581..b9d5e7c9ef43 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -684,8 +684,6 @@ void *__init_or_module text_poke_early(void *addr, const void *opcode,
  * 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: Must be called under text_mutex.
  */
 void *text_poke(void *addr, const void *opcode, size_t len)
 {
@@ -700,6 +698,8 @@ void *text_poke(void *addr, const void *opcode, size_t len)
 	 */
 	BUG_ON(!after_bootmem);
 
+	lockdep_assert_held(&text_mutex);
+
 	if (!core_kernel_text((unsigned long)addr)) {
 		pages[0] = vmalloc_to_page(addr);
 		pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
@@ -782,8 +782,6 @@ int poke_int3_handler(struct pt_regs *regs)
  *	- replace the first byte (int3) by the first byte of
  *	  replacing opcode
  *	- sync cores
- *
- * Note: must be called under text_mutex.
  */
 void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
 {
@@ -792,6 +790,9 @@ void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
 	bp_int3_handler = handler;
 	bp_int3_addr = (u8 *)addr + sizeof(int3);
 	bp_patching_in_progress = true;
+
+	lockdep_assert_held(&text_mutex);
+
 	/*
 	 * Corresponding read barrier in int3 notifier for making sure the
 	 * in_progress and handler are correctly ordered wrt. patching.