[PATCH 4.9 46/74] s390: correct module section names for expoline code revert

From: Greg Kroah-Hartman
Date: Fri Apr 27 2018 - 11:08:49 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>

[ 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@xxxxxxxxxxxxxxx # 4.16
Fixes: f19fbd5ed6 ("s390: introduce execute-trampolines for branches")
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
arch/s390/kernel/module.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/s390/kernel/module.c
+++ b/arch/s390/kernel/module.c
@@ -477,11 +477,11 @@ int module_finalize(const Elf_Ehdr *hdr,
apply_alternatives(aseg, aseg + s->sh_size);

- (!strcmp(".nospec_call_table", secname)))
+ (!strncmp(".s390_indirect", secname, 14)))
nospec_revert(aseg, aseg + s->sh_size);

- (!strcmp(".nospec_return_table", secname)))
+ (!strncmp(".s390_return", secname, 12)))
nospec_revert(aseg, aseg + s->sh_size);