Use lockdep to ensure that text_mutex is taken when text_poke() is
called.
Actually it is not always taken, specifically when it is called by kgdb,
so take the lock in these cases.
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Nadav Amit <namit@xxxxxxxxxx>
---
arch/x86/kernel/alternative.c | 1 +
arch/x86/kernel/kgdb.c | 9 +++++++++
2 files changed, 10 insertions(+)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 014f214da581..916c11b410c4 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -699,6 +699,7 @@ void *text_poke(void *addr, const void *opcode, size_t len)
* pages as they are not yet initialized.
*/
BUG_ON(!after_bootmem);
+ lockdep_assert_held(&text_mutex);
if (!core_kernel_text((unsigned long)addr)) {
pages[0] = vmalloc_to_page(addr);
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 8e36f249646e..60b99c76086c 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -768,8 +768,12 @@ int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
*/
if (mutex_is_locked(&text_mutex))
return -EBUSY;
+
+ /* Take the mutex to avoid lockdep assertion failures. */
+ mutex_lock(&text_mutex);
text_poke((void *)bpt->bpt_addr, arch_kgdb_ops.gdb_bpt_instr,
BREAK_INSTR_SIZE);
+ mutex_unlock(&text_mutex);
err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
if (err)
return err;
@@ -793,7 +797,12 @@ int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
*/
if (mutex_is_locked(&text_mutex))
goto knl_write;
+
+ /* Take the mutex to avoid lockdep assertion failures. */
+ mutex_lock(&text_mutex);
text_poke((void *)bpt->bpt_addr, bpt->saved_instr, BREAK_INSTR_SIZE);
+ mutex_unlock(&text_mutex);
+
err = probe_kernel_read(opc, (char *)bpt->bpt_addr, BREAK_INSTR_SIZE);
if (err || memcmp(opc, bpt->saved_instr, BREAK_INSTR_SIZE))
goto knl_write;
--
2.17.1
