[PATCH v2 07/10] s390/nospec-branch: Serialize text patching with text_mutex

[Heiko Carstens]

Acquire text_mutex inside __nospec_revert() around the patching loop.

Serialization is not required for __nospec_revert(), however this is
part of larger series where at the end s390_kernel_write() requires
that callers hold text_mutex.

Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx>
---
 arch/s390/kernel/nospec-branch.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/s390/kernel/nospec-branch.c b/arch/s390/kernel/nospec-branch.c
index e11ec15960a1..26cd5b278e8a 100644
--- a/arch/s390/kernel/nospec-branch.c
+++ b/arch/s390/kernel/nospec-branch.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/memory.h>
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/cpu.h>
@@ -108,6 +109,7 @@ static void __init_or_module __nospec_revert(s32 *start, s32 *end)
 
 	/* Second part of the instruction replace is always a nop */
 	memcpy(insnbuf + 2, branch, sizeof(branch));
+	guard(mutex)(&text_mutex);
 	for (epo = start; epo < end; epo++) {
 		instr = (u8 *) epo + *epo;
 		if (instr[0] == 0xc0 && (instr[1] & 0x0f) == 0x04)
-- 
2.53.0