[PATCH] powerpc/pkeys: preallocate execute_only key only if the key is available.
From: Ram Pai <hidden>
Date: 2018-06-20 05:34:58
Key 2 is preallocated and reserved for execute-only key. In rare cases if key-2 is unavailable, mprotect(PROT_EXEC) will behave incorrectly. NOTE: mprotect(PROT_EXEC) uses execute-only key. Ensure key 2 is available for preallocation before reserving it for execute_only purpose. CC: Michael Ellerman <mpe@ellerman.id.au> CC: Thiago Jung Bauermann <redacted> Signed-off-by: Ram Pai <redacted> --- arch/powerpc/mm/pkeys.c | 14 +++++++++----- 1 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c
index cec990c..2013ef0 100644
--- a/arch/powerpc/mm/pkeys.c
+++ b/arch/powerpc/mm/pkeys.c@@ -19,6 +19,7 @@ u64 pkey_amr_mask; /* Bits in AMR not to be touched */ u64 pkey_iamr_mask; /* Bits in AMR not to be touched */ u64 pkey_uamor_mask; /* Bits in UMOR not to be touched */ +u32 execute_only_key = 2; #define AMR_BITS_PER_PKEY 2 #define AMR_RD_BIT 0x1UL
@@ -26,7 +27,6 @@ #define IAMR_EX_BIT 0x1UL #define PKEY_REG_BITS (sizeof(u64)*8) #define pkeyshift(pkey) (PKEY_REG_BITS - ((pkey+1) * AMR_BITS_PER_PKEY)) -#define EXECUTE_ONLY_KEY 2 static void scan_pkey_feature(void) {
@@ -122,8 +122,12 @@ int pkey_initialize(void) #else os_reserved = 0; #endif + + if ((pkeys_total - os_reserved) <= execute_only_key) + execute_only_key = -1; + /* Bits are in LE format. */ - reserved_allocation_mask = (0x1 << 1) | (0x1 << EXECUTE_ONLY_KEY); + reserved_allocation_mask = (0x1 << 1) | (0x1 << execute_only_key); initial_allocation_mask = reserved_allocation_mask | (0x1 << PKEY_0); /* register mask is in BE format */
@@ -132,11 +136,11 @@ int pkey_initialize(void) pkey_iamr_mask = ~0x0ul; pkey_iamr_mask &= ~(0x3ul << pkeyshift(PKEY_0)); - pkey_iamr_mask &= ~(0x3ul << pkeyshift(EXECUTE_ONLY_KEY)); + pkey_iamr_mask &= ~(0x3ul << pkeyshift(execute_only_key)); pkey_uamor_mask = ~0x0ul; pkey_uamor_mask &= ~(0x3ul << pkeyshift(PKEY_0)); - pkey_uamor_mask &= ~(0x3ul << pkeyshift(EXECUTE_ONLY_KEY)); + pkey_uamor_mask &= ~(0x3ul << pkeyshift(execute_only_key)); for (i = (pkeys_total - os_reserved); i < pkeys_total; i++) pkey_uamor_mask &= ~(0x3ul << pkeyshift(i));
@@ -151,7 +155,7 @@ void pkey_mm_init(struct mm_struct *mm) if (static_branch_likely(&pkey_disabled)) return; mm_pkey_allocation_map(mm) = initial_allocation_mask; - mm->context.execute_only_pkey = EXECUTE_ONLY_KEY; + mm->context.execute_only_pkey = execute_only_key; } static inline u64 read_amr(void)
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1.7.1