[RFC PATCH 1/6] x86/alternative: assert text_mutex is taken
From: Nadav Amit <hidden>
Date: 2018-08-29 08:13:31
Also in:
lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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@kernel.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Kees Cook <redacted> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Nadav Amit <redacted> --- 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