| Message ID | 1529472862-26506-1-git-send-email-linuxram@us.ibm.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Headers | show |
| Series | powerpc/pkeys: preallocate execute_only key only if the key is available. | expand |
On Tue, Jun 19, 2018 at 10:34:22PM -0700, Ram Pai wrote: > 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 <bauerman@linux.ibm.com> > Signed-off-by: Ram Pai <linuxram@us.ibm.com> > --- > 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; this cannot be unsigned, since it can get set to -1 if key 2 is not available. :( Please ignore this patch. Will resend a fixed version. > > #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; > + .snip.. RP
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)
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 <bauerman@linux.ibm.com> Signed-off-by: Ram Pai <linuxram@us.ibm.com> --- arch/powerpc/mm/pkeys.c | 14 +++++++++----- 1 files changed, 9 insertions(+), 5 deletions(-)