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x86/CPU/AMD: Do not leak quotient data after a division by 0

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commit 77245f1c3c6495521f6a3af082696ee2f8ce3921 upstream.

Under certain circumstances, an integer division by 0 which faults, can
leave stale quotient data from a previous division operation on Zen1
microarchitectures.

Do a dummy division 0/1 before returning from the #DE exception handler
in order to avoid any leaks of potentially sensitive data.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov (AMD)
2023-08-05 00:06:43 +02:00
committed by Greg Kroah-Hartman
parent 98b7ab5e8d
commit b6fc2fbf89
4 changed files with 24 additions and 0 deletions
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2
arch/x86/include/asm/processor.h
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@@ -809,10 +809,12 @@ DECLARE_PER_CPU(u64, msr_misc_features_shadow);
extern u16 amd_get_nb_id(int cpu);
extern u32 amd_get_nodes_per_socket(void);
extern bool cpu_has_ibpb_brtype_microcode(void);
extern void amd_clear_divider(void);
#else
static inline u16 amd_get_nb_id(int cpu) { return 0; }
static inline u32 amd_get_nodes_per_socket(void) { return 0; }
static inline bool cpu_has_ibpb_brtype_microcode(void) { return false; }
static inline void amd_clear_divider(void) { }
#endif
static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)