From: Josh Poimboeuf jpoimboe@kernel.org
commit c9305b6c1f52060377c72aebe3a701389e9f3172 upstream.
Add proper alignment for .nospec_call_table and .nospec_return_table in vmlinux.
[hca@linux.ibm.com]: The problem with the missing alignment of the nospec tables exist since a long time, however only since commit e6ed91fd0768 ("s390/alternatives: remove padding generation code") and with CONFIG_RELOCATABLE=n the kernel may also crash at boot time.
The above named commit reduced the size of struct alt_instr by one byte, so its new size is 11 bytes. Therefore depending on the number of cpu alternatives the size of the __alt_instructions array maybe odd, which again also causes that the addresses of the nospec tables will be odd.
If the address of __nospec_call_start is odd and the kernel is compiled With CONFIG_RELOCATABLE=n the compiler may generate code that loads the address of __nospec_call_start with a 'larl' instruction.
This will generate incorrect code since the 'larl' instruction only works with even addresses. In result the members of the nospec tables will be accessed with an off-by-one offset, which subsequently may lead to addressing exceptions within __nospec_revert().
Fixes: f19fbd5ed642 ("s390: introduce execute-trampolines for branches") Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Link: https://lore.kernel.org/r/8719bf1ce4a72ebdeb575200290094e9ce047bcc.166155733... Cc: stable@vger.kernel.org # 4.16 Reviewed-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/kernel/vmlinux.lds.S | 1 + 1 file changed, 1 insertion(+)
--- a/arch/s390/kernel/vmlinux.lds.S +++ b/arch/s390/kernel/vmlinux.lds.S @@ -122,6 +122,7 @@ SECTIONS /* * Table with the patch locations to undo expolines */ + . = ALIGN(4); .nospec_call_table : { __nospec_call_start = . ; *(.s390_indirect*)