[PATCH 5.6 106/126] s390/kaslr: add support for R_390_JMP_SLOT relocation type

From: Greg Kroah-Hartman
Date: Tue May 26 2020 - 15:15:19 EST

From: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>

commit 4c1cbcbd6c56c79de2c07159be4f55386bb0bef2 upstream.

With certain kernel configurations, the R_390_JMP_SLOT relocation type
might be generated, which is not expected by the KASLR relocation code,
and the kernel stops with the message "Unknown relocation type".

This was found with a zfcpdump kernel config, where CONFIG_MODULES=n
and CONFIG_VFIO=n. In that case, symbol_get() is used on undefined
__weak symbols in virt/kvm/vfio.c, which results in the generation
of R_390_JMP_SLOT relocation types.

Fix this by handling R_390_JMP_SLOT similar to R_390_GLOB_DAT.

Fixes: 805bc0bc238f ("s390/kernel: build a relocatable kernel")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.2+
Signed-off-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Reviewed-by: Philipp Rudo <prudo@xxxxxxxxxxxxx>
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/s390/kernel/machine_kexec_reloc.c | 1 +
1 file changed, 1 insertion(+)

--- a/arch/s390/kernel/machine_kexec_reloc.c
+++ b/arch/s390/kernel/machine_kexec_reloc.c
@@ -28,6 +28,7 @@ int arch_kexec_do_relocs(int r_type, voi
case R_390_64: /* Direct 64 bit. */
case R_390_GLOB_DAT:
+ case R_390_JMP_SLOT:
*(u64 *)loc = val;
case R_390_PC16: /* PC relative 16 bit. */