Messages in this thread Patch in this message | | | From | Andrew Cooper <> | Subject | [PATCH] x86/pkey: Fix undefined behaviour with PKRU_WD_BIT | Date | Thu, 16 Dec 2021 00:08:56 +0000 |
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Both __pkru_allows_write() and arch_set_user_pkey_access() shift PKRU_WD_BIT (a signed constant) by up to 30 bits, hitting the sign bit.
Use unsigned constants instead.
Clearly pkey 15 has not been used in combination with UBSAN yet.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Thomas Gleixner <tglx@linutronix.de> CC: Ingo Molnar <mingo@redhat.com> CC: Borislav Petkov <bp@alien8.de> CC: Dave Hansen <dave.hansen@linux.intel.com> CC: x86@kernel.org CC: "H. Peter Anvin" <hpa@zytor.com>
Noticed by code inspection only. I can't actually provoke the compiler into generating incorrect logic as far as this shift is concerned, so haven't included a fixes tag.
If wanted, it is:
Fixes: 33a709b25a76 ("mm/gup, x86/mm/pkeys: Check VMAs and PTEs for protection keys")
except it will collide with the very recent code movement in 784a46618f634. --- arch/x86/include/asm/pkru.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/pkru.h b/arch/x86/include/asm/pkru.h index 4cd49afa0ca4..74f0a2d34ffd 100644 --- a/arch/x86/include/asm/pkru.h +++ b/arch/x86/include/asm/pkru.h @@ -4,8 +4,8 @@ #include <asm/cpufeature.h> -#define PKRU_AD_BIT 0x1 -#define PKRU_WD_BIT 0x2 +#define PKRU_AD_BIT 0x1u +#define PKRU_WD_BIT 0x2u #define PKRU_BITS_PER_PKEY 2 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS -- 2.11.0
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