linux-kernel - [PATCH 5.6 106/126] s390/kaslr: add support for R_390_JMP

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Message-Id: <20200526183946.546777067@linuxfoundation.org>
Date:   Tue, 26 May 2020 20:54:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Philipp Rudo <prudo@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>
Subject: [PATCH 5.6 106/126] s390/kaslr: add support for R_390_JMP_SLOT relocation type

From: Gerald Schaefer <gerald.schaefer@...ibm.com>

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@...r.kernel.org> # v5.2+
Signed-off-by: Gerald Schaefer <gerald.schaefer@...ibm.com>
Reviewed-by: Philipp Rudo <prudo@...ux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@...ux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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
 		break;
 	case R_390_64:		/* Direct 64 bit.  */
 	case R_390_GLOB_DAT:
+	case R_390_JMP_SLOT:
 		*(u64 *)loc = val;
 		break;
 	case R_390_PC16:	/* PC relative 16 bit.	*/