[SRU][Bionic][PATCH 2/2] arm64: add sentinel to kpti_safe_list

[Juerg Haefliger]

From: Mark Rutland <mark.rutland at arm.com>

BugLink: https://bugs.launchpad.net/bugs/1857074
BugLink: https://bugs.launchpad.net/bugs/1853485
BugLink: https://bugs.launchpad.net/bugs/1853326

We're missing a sentinel entry in kpti_safe_list. Thus is_midr_in_range_list()
can walk past the end of kpti_safe_list. Depending on the contents of memory,
this could erroneously match a CPU's MIDR, cause a data abort, or other bad
outcomes.

Add the sentinel entry to avoid this.

Fixes: be5b299830c63ed7 ("arm64: capabilities: Add support for checks based on a list of MIDRs")
Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Reported-by: Jan Kiszka <jan.kiszka at siemens.com>
Tested-by: Jan Kiszka <jan.kiszka at siemens.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Suzuki K Poulose <suzuki.poulose at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>

(backported from commit 71c751f2a43fa03fae3cf5f0067ed3001a397013)
[juergh: Adjusted context.]
Signed-off-by: Juerg Haefliger <juergh at canonical.com>
---
 arch/arm64/kernel/cpufeature.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 3d332823ba93..c9474f33549f 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -897,6 +897,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry,
 		MIDR_ALL_VERSIONS(MIDR_CORTEX_A72),
 		MIDR_ALL_VERSIONS(MIDR_CORTEX_A73),
 		MIDR_ALL_VERSIONS(MIDR_HISI_TSV110),
+		{ /* sentinel */ }
 	};
 	char const *str = "kpti command line option";
 	bool meltdown_safe;
-- 
2.20.1