Commit c27c753e authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

x86/static_call: Serialize __static_call_fixup() properly 



__static_call_fixup() invokes __static_call_transform() without holding
text_mutex, which causes lockdep to complain in text_poke_bp().

Adding the proper locking cures that, but as this is either used during
early boot or during module finalizing, it's not required to use
text_poke_bp(). Add an argument to __static_call_transform() which tells
it to use text_poke_early() for it.

Fixes: ee88d363 ("x86,static_call: Use alternative RET encoding")
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent f43b9876

arch/x86/kernel/static_call.c

+8 −5
Original line number Diff line number Diff line
@@ -25,7 +25,8 @@ static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 }; 


static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc };



static void __ref __static_call_transform(void *insn, enum insn_type type, void *func)

static void __ref __static_call_transform(void *insn, enum insn_type type,

					  void *func, bool modinit)

{

	const void *emulate = NULL;

	int size = CALL_INSN_SIZE;
@@ -60,7 +61,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void 
	if (memcmp(insn, code, size) == 0)

		return;



	if (unlikely(system_state == SYSTEM_BOOTING))

	if (system_state == SYSTEM_BOOTING || modinit)

		return text_poke_early(insn, code, size);



	text_poke_bp(insn, code, size, emulate);
@@ -114,12 +115,12 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail) 


	if (tramp) {

		__static_call_validate(tramp, true, true);

		__static_call_transform(tramp, __sc_insn(!func, true), func);

		__static_call_transform(tramp, __sc_insn(!func, true), func, false);

	}



	if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) {

		__static_call_validate(site, tail, false);

		__static_call_transform(site, __sc_insn(!func, tail), func);

		__static_call_transform(site, __sc_insn(!func, tail), func, false);

	}



	mutex_unlock(&text_mutex);
@@ -145,8 +146,10 @@ bool __static_call_fixup(void *tramp, u8 op, void *dest) 
		return false;

	}



	mutex_lock(&text_mutex);

	if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk)

		__static_call_transform(tramp, RET, NULL);

		__static_call_transform(tramp, RET, NULL, true);

	mutex_unlock(&text_mutex);



	return true;

}