Messages in this thread Patch in this message | | | From | Alex Thorlton <> | Subject | [PATCH] Skip UV runtime services mapping in the efi_runtime_disabled case | Date | Tue, 26 Jul 2016 17:38:33 -0500 |
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This problem has actually been in the UV code for a while, but we didn't catch it until recently, because we had been relying on EFI_OLD_MEMMAP to allow our systems to boot for a period of time. We noticed the issue when trying to kexec a recent community kernel, where we hit this NULL pointer dereference in efi_sync_low_kernel_mappings:
[ 0.337515] BUG: unable to handle kernel NULL pointer dereference at 0000000000000880 [ 0.346276] IP: [<ffffffff8105df8d>] efi_sync_low_kernel_mappings+0x5d/0x1b0
The problem doesn't show up with EFI_OLD_MEMMAP because we skip the chunk of setup_efi_state that sets the efi_loader_signature for the kexec'd kernel. When the kexec'd kernel boots, it won't set EFI_BOOT in setup_arch, so we completely avoid the bug.
We always kexec with noefi on the command line, so this shouldn't be an issue, but since we're not actually checking for efi_runtime_disabled in uv_bios_init, we end up trying to do EFI runtime callbacks when we shouldn't be. This patch just adds a check for efi_runtime_disabled in uv_bios_init so that we don't map in uv_systab when runtime_disabled == true.
Signed-off-by: Alex Thorlton <athorlton@sgi.com> Cc: Russ Anderson <rja@sgi.com> Cc: Mike Travis <travis@sgi.com> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Borislav Petkov <bp@suse.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: x86@kernel.org --- arch/x86/platform/uv/bios_uv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c index 66b2166..0df8a03 100644 --- a/arch/x86/platform/uv/bios_uv.c +++ b/arch/x86/platform/uv/bios_uv.c @@ -187,7 +187,8 @@ EXPORT_SYMBOL_GPL(uv_bios_set_legacy_vga_target); void uv_bios_init(void) { uv_systab = NULL; - if ((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || !efi.uv_systab) { + if ((efi.uv_systab == EFI_INVALID_TABLE_ADDR) || + !efi.uv_systab || efi_runtime_disabled()) { pr_crit("UV: UVsystab: missing\n"); return; } -- 1.8.5.6
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