s390: correct module section names for expoline code revert

BugLink: http://bugs.launchpad.net/bugs/1775483
[ Upstream commit 6cf09958f32b9667bb3ebadf74367c791112771b ]

The main linker script vmlinux.lds.S for the kernel image merges
the expoline code patch tables into two section ".nospec_call_table"
and ".nospec_return_table". This is *not* done for the modules,
there the sections retain their original names as generated by gcc:
".s390_indirect_call", ".s390_return_mem" and ".s390_return_reg".

The module_finalize code has to check for the compiler generated
section names, otherwise no code patching is done. This slows down
the module code in case of "spectre_v2=off".

Cc: stable@vger.kernel.org # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
index 5a83be955c70ed8f9a378ec6a47c61933c2968d9..0dc8ac8548ee3f32904038b41b5b30517516bf41 100644 (file)
--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -465,11 +465,11 @@ int module_finalize(const Elf_Ehdr *hdr,
                        apply_alternatives(aseg, aseg + s->sh_size);
 
                if (IS_ENABLED(CONFIG_EXPOLINE) &&
-                   (!strcmp(".nospec_call_table", secname)))
+                   (!strncmp(".s390_indirect", secname, 14)))
                        nospec_revert(aseg, aseg + s->sh_size);
 
                if (IS_ENABLED(CONFIG_EXPOLINE) &&
-                   (!strcmp(".nospec_return_table", secname)))
+                   (!strncmp(".s390_return", secname, 12)))
                        nospec_revert(aseg, aseg + s->sh_size);
        }