(backport only)

We're about to grow the exception handlers, which will make a bunch of them no longer fit within the space available. We move them out of line.

This is a fiddly and error-prone business, so in the interests of reviewability I haven't merged this in with the addition of the entry flush.

Signed-off-by: Daniel Axtens dja@axtens.net --- arch/powerpc/kernel/exceptions-64s.S | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index e1dab9b1e447..fcf459694ccb 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -572,13 +572,16 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX) EXC_REAL_BEGIN(data_access_slb, 0x380, 0x80) SET_SCRATCH0(r13) EXCEPTION_PROLOG_0(PACA_EXSLB) + b tramp_data_access_slb +EXC_REAL_END(data_access_slb, 0x380, 0x80) + +TRAMP_REAL_BEGIN(tramp_data_access_slb) EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST_PR, 0x380) mr r12,r3 /* save r3 */ mfspr r3,SPRN_DAR mfspr r11,SPRN_SRR1 crset 4*cr6+eq BRANCH_TO_COMMON(r10, slb_miss_common) -EXC_REAL_END(data_access_slb, 0x380, 0x80)

EXC_VIRT_BEGIN(data_access_slb, 0x4380, 0x80) SET_SCRATCH0(r13) @@ -616,13 +619,16 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX) EXC_REAL_BEGIN(instruction_access_slb, 0x480, 0x80) SET_SCRATCH0(r13) EXCEPTION_PROLOG_0(PACA_EXSLB) + b tramp_instruction_access_slb +EXC_REAL_END(instruction_access_slb, 0x480, 0x80) + +TRAMP_REAL_BEGIN(tramp_instruction_access_slb) EXCEPTION_PROLOG_1(PACA_EXSLB, KVMTEST_PR, 0x480) mr r12,r3 /* save r3 */ mfspr r3,SPRN_SRR0 /* SRR0 is faulting address */ mfspr r11,SPRN_SRR1 crclr 4*cr6+eq BRANCH_TO_COMMON(r10, slb_miss_common) -EXC_REAL_END(instruction_access_slb, 0x480, 0x80)

EXC_VIRT_BEGIN(instruction_access_slb, 0x4480, 0x80) SET_SCRATCH0(r13)

From: Christophe Leroy christophe.leroy@c-s.fr

Backported from commit de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection"). Here we don't try to add the KUAP framework, we just want the helper functions because we want to put uaccess flush helpers in them.

In terms of fixes, we don't need commit 1d8f739b07bd ("powerpc/kuap: Fix set direction in allow/prevent_user_access()") as we don't have real KUAP. Likewise as all our allows are noops and all our prevents are just flushes, we don't need commit 9dc086f1e9ef ("powerpc/futex: Fix incorrect user access blocking") The other 2 fixes we do need.

The original description is:

This patch implements a framework for Kernel Userspace Access Protection.

Then subarches will have the possibility to provide their own implementation by providing setup_kuap() and allow/prevent_user_access().

Some platforms will need to know the area accessed and whether it is accessed from read, write or both. Therefore source, destination and size and handed over to the two functions.

mpe: Rename to allow/prevent rather than unlock/lock, and add read/write wrappers. Drop the 32-bit code for now until we have an implementation for it. Add kuap to pt_regs for 64-bit as well as 32-bit. Don't split strings, use pr_crit_ratelimited().

Signed-off-by: Christophe Leroy christophe.leroy@c-s.fr Signed-off-by: Russell Currey ruscur@russell.cc Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Daniel Axtens dja@axtens.net --- arch/powerpc/include/asm/futex.h | 4 +++ arch/powerpc/include/asm/kup.h | 36 ++++++++++++++++++++++++++ arch/powerpc/include/asm/uaccess.h | 38 ++++++++++++++++++++++------ arch/powerpc/lib/checksum_wrappers.c | 4 +++ 4 files changed, 74 insertions(+), 8 deletions(-) create mode 100644 arch/powerpc/include/asm/kup.h

diff --git a/arch/powerpc/include/asm/futex.h b/arch/powerpc/include/asm/futex.h index 2a7b01f97a56..1eabc20dddd3 100644 --- a/arch/powerpc/include/asm/futex.h +++ b/arch/powerpc/include/asm/futex.h @@ -35,6 +35,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval, { int oldval = 0, ret;

+ allow_write_to_user(uaddr, sizeof(*uaddr)); pagefault_disable();

switch (op) { @@ -61,6 +62,7 @@ static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,

*oval = oldval;

+ prevent_write_to_user(uaddr, sizeof(*uaddr)); return ret; }

@@ -74,6 +76,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) return -EFAULT;

+ allow_write_to_user(uaddr, sizeof(*uaddr)); __asm__ __volatile__ ( PPC_ATOMIC_ENTRY_BARRIER "1: lwarx %1,0,%3 # futex_atomic_cmpxchg_inatomic\n\ @@ -94,6 +97,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, : "cc", "memory");

*uval = prev; + prevent_write_to_user(uaddr, sizeof(*uaddr)); return ret; }

diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h new file mode 100644 index 000000000000..7895d5eeaf21 --- /dev/null +++ b/arch/powerpc/include/asm/kup.h @@ -0,0 +1,36 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_POWERPC_KUP_H_ +#define _ASM_POWERPC_KUP_H_ + +#ifndef __ASSEMBLY__ + +#include <asm/pgtable.h> + +static inline void allow_user_access(void __user *to, const void __user *from, + unsigned long size) { } +static inline void prevent_user_access(void __user *to, const void __user *from, + unsigned long size) { } + +static inline void allow_read_from_user(const void __user *from, unsigned long size) +{ + allow_user_access(NULL, from, size); +} + +static inline void allow_write_to_user(void __user *to, unsigned long size) +{ + allow_user_access(to, NULL, size); +} + +static inline void prevent_read_from_user(const void __user *from, unsigned long size) +{ + prevent_user_access(NULL, from, size); +} + +static inline void prevent_write_to_user(void __user *to, unsigned long size) +{ + prevent_user_access(to, NULL, size); +} + +#endif /* !__ASSEMBLY__ */ + +#endif /* _ASM_POWERPC_KUP_H_ */ diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 38a25ff8afb7..b604bb140a30 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -6,6 +6,7 @@ #include <asm/processor.h> #include <asm/page.h> #include <asm/extable.h> +#include <asm/kup.h>

/* * The fs value determines whether argument validity checking should be @@ -141,6 +142,7 @@ extern long __put_user_bad(void); #define __put_user_size(x, ptr, size, retval) \ do { \ retval = 0; \ + allow_write_to_user(ptr, size); \ switch (size) { \ case 1: __put_user_asm(x, ptr, retval, "stb"); break; \ case 2: __put_user_asm(x, ptr, retval, "sth"); break; \ @@ -148,6 +150,7 @@ do { \ case 8: __put_user_asm2(x, ptr, retval); break; \ default: __put_user_bad(); \ } \ + prevent_write_to_user(ptr, size); \ } while (0)

#define __put_user_nocheck(x, ptr, size) \ @@ -240,6 +243,7 @@ do { \ __chk_user_ptr(ptr); \ if (size > sizeof(x)) \ (x) = __get_user_bad(); \ + allow_read_from_user(ptr, size); \ switch (size) { \ case 1: __get_user_asm(x, ptr, retval, "lbz"); break; \ case 2: __get_user_asm(x, ptr, retval, "lhz"); break; \ @@ -247,6 +251,7 @@ do { \ case 8: __get_user_asm2(x, ptr, retval); break; \ default: (x) = __get_user_bad(); \ } \ + prevent_read_from_user(ptr, size); \ } while (0)

/* @@ -306,16 +311,22 @@ extern unsigned long __copy_tofrom_user(void __user *to, static inline unsigned long raw_copy_in_user(void __user *to, const void __user *from, unsigned long n) { + unsigned long ret; + barrier_nospec(); - return __copy_tofrom_user(to, from, n); + allow_user_access(to, from, n); + ret = __copy_tofrom_user(to, from, n); + prevent_user_access(to, from, n); + return ret; } #endif /* __powerpc64__ */

static inline unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n) { + unsigned long ret; if (__builtin_constant_p(n) && (n <= 8)) { - unsigned long ret = 1; + ret = 1;

switch (n) { case 1: @@ -340,14 +351,18 @@ static inline unsigned long raw_copy_from_user(void *to, }

barrier_nospec(); - return __copy_tofrom_user((__force void __user *)to, from, n); + allow_read_from_user(from, n); + ret = __copy_tofrom_user((__force void __user *)to, from, n); + prevent_read_from_user(from, n); + return ret; }

static inline unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n) { + unsigned long ret; if (__builtin_constant_p(n) && (n <= 8)) { - unsigned long ret = 1; + ret = 1;

switch (n) { case 1: @@ -367,17 +382,24 @@ static inline unsigned long raw_copy_to_user(void __user *to, return 0; }

- return __copy_tofrom_user(to, (__force const void __user *)from, n); + allow_write_to_user(to, n); + ret = __copy_tofrom_user(to, (__force const void __user *)from, n); + prevent_write_to_user(to, n); + return ret; }

extern unsigned long __clear_user(void __user *addr, unsigned long size);

static inline unsigned long clear_user(void __user *addr, unsigned long size) { + unsigned long ret = size; might_fault(); - if (likely(access_ok(VERIFY_WRITE, addr, size))) - return __clear_user(addr, size); - return size; + if (likely(access_ok(VERIFY_WRITE, addr, size))) { + allow_write_to_user(addr, size); + ret = __clear_user(addr, size); + prevent_write_to_user(addr, size); + } + return ret; }

extern long strncpy_from_user(char *dst, const char __user *src, long count); diff --git a/arch/powerpc/lib/checksum_wrappers.c b/arch/powerpc/lib/checksum_wrappers.c index a0cb63fb76a1..8d83c39be7e4 100644 --- a/arch/powerpc/lib/checksum_wrappers.c +++ b/arch/powerpc/lib/checksum_wrappers.c @@ -29,6 +29,7 @@ __wsum csum_and_copy_from_user(const void __user *src, void *dst, unsigned int csum;

might_sleep(); + allow_read_from_user(src, len);

*err_ptr = 0;

@@ -60,6 +61,7 @@ __wsum csum_and_copy_from_user(const void __user *src, void *dst, }

out: + prevent_read_from_user(src, len); return (__force __wsum)csum; } EXPORT_SYMBOL(csum_and_copy_from_user); @@ -70,6 +72,7 @@ __wsum csum_and_copy_to_user(const void *src, void __user *dst, int len, unsigned int csum;

might_sleep(); + allow_write_to_user(dst, len);

*err_ptr = 0;

@@ -97,6 +100,7 @@ __wsum csum_and_copy_to_user(const void *src, void __user *dst, int len, }

out: + prevent_write_to_user(dst, len); return (__force __wsum)csum; } EXPORT_SYMBOL(csum_and_copy_to_user);

From: Andrew Donnellan ajd@linux.ibm.com

commit 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 upstream.

The KUAP implementation adds calls in clear_user() to enable and disable access to userspace memory. However, it doesn't add these to __clear_user(), which is used in the ptrace regset code.

As there's only one direct user of __clear_user() (the regset code), and the time taken to set the AMR for KUAP purposes is going to dominate the cost of a quick access_ok(), there's not much point having a separate path.

Rename __clear_user() to __arch_clear_user(), and make __clear_user() just call clear_user().

Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com Reported-by: Daniel Axtens dja@axtens.net Suggested-by: Michael Ellerman mpe@ellerman.id.au Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan ajd@linux.ibm.com [mpe: Use __arch_clear_user() for the asm version like arm64 & nds32] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com Signed-off-by: Daniel Axtens dja@axtens.net --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/lib/string_32.S | 4 ++-- arch/powerpc/lib/string_64.S | 6 +++--- 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 463e3d3dd0a3..15d9706a9f9c 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -416,7 +416,7 @@ raw_copy_to_user(void __user *to, const void *from, unsigned long n) return ret; }

-extern unsigned long __clear_user(void __user *addr, unsigned long size); +unsigned long __arch_clear_user(void __user *addr, unsigned long size);

static inline unsigned long clear_user(void __user *addr, unsigned long size) { @@ -424,12 +424,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size) might_fault(); if (likely(access_ok(VERIFY_WRITE, addr, size))) { allow_write_to_user(addr, size); - ret = __clear_user(addr, size); + ret = __arch_clear_user(addr, size); prevent_write_to_user(addr, size); } return ret; }

+static inline unsigned long __clear_user(void __user *addr, unsigned long size) +{ + return clear_user(addr, size); +} + extern long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strnlen_user(const char __user *str, long n);

diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S index f69a6aab7bfb..1ddb26394e8a 100644 --- a/arch/powerpc/lib/string_32.S +++ b/arch/powerpc/lib/string_32.S @@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES LG_CACHELINE_BYTES = L1_CACHE_SHIFT CACHELINE_MASK = (L1_CACHE_BYTES-1)

-_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) /* * Use dcbz on the complete cache lines in the destination * to set them to zero. This requires that the destination @@ -87,4 +87,4 @@ _GLOBAL(__clear_user) EX_TABLE(8b, 91b) EX_TABLE(9b, 91b)

-EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user) diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S index 56aac4c22025..ea3798f4f25f 100644 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -29,7 +29,7 @@ PPC64_CACHES: .section ".text"

/** - * __clear_user: - Zero a block of memory in user space, with less checking. + * __arch_clear_user: - Zero a block of memory in user space, with less checking. * @to: Destination address, in user space. * @n: Number of bytes to zero. * @@ -70,7 +70,7 @@ err3; stb r0,0(r3) mr r3,r4 blr

-_GLOBAL_TOC(__clear_user) +_GLOBAL_TOC(__arch_clear_user) cmpdi r4,32 neg r6,r3 li r0,0 @@ -193,4 +193,4 @@ err1; dcbz 0,r3 cmpdi r4,32 blt .Lshort_clear b .Lmedium_clear -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user)

From: Nicholas Piggin npiggin@gmail.com

commit 9a32a7e78bd0cd9a9b6332cbdc345ee5ffd0c5de upstream.

IBM Power9 processors can speculatively operate on data in the L1 cache before it has been completely validated, via a way-prediction mechanism. It is not possible for an attacker to determine the contents of impermissible memory using this method, since these systems implement a combination of hardware and software security measures to prevent scenarios where protected data could be leaked.

However these measures don't address the scenario where an attacker induces the operating system to speculatively execute instructions using data that the attacker controls. This can be used for example to speculatively bypass "kernel user access prevention" techniques, as discovered by Anthony Steinhauser of Google's Safeside Project. This is not an attack by itself, but there is a possibility it could be used in conjunction with side-channels or other weaknesses in the privileged code to construct an attack.

This issue can be mitigated by flushing the L1 cache between privilege boundaries of concern. This patch flushes the L1 cache after user accesses.

This is part of the fix for CVE-2020-4788.

Signed-off-by: Nicholas Piggin npiggin@gmail.com Signed-off-by: Daniel Axtens dja@axtens.net --- .../admin-guide/kernel-parameters.txt | 4 + .../powerpc/include/asm/book3s/64/kup-radix.h | 22 +++++ arch/powerpc/include/asm/feature-fixups.h | 9 +++ arch/powerpc/include/asm/kup.h | 4 + arch/powerpc/include/asm/security_features.h | 3 + arch/powerpc/include/asm/setup.h | 1 + arch/powerpc/kernel/exceptions-64s.S | 81 ++++++------------- arch/powerpc/kernel/setup_64.c | 62 ++++++++++++++ arch/powerpc/kernel/vmlinux.lds.S | 7 ++ arch/powerpc/lib/feature-fixups.c | 50 ++++++++++++ arch/powerpc/platforms/powernv/setup.c | 10 ++- arch/powerpc/platforms/pseries/setup.c | 4 + 12 files changed, 198 insertions(+), 59 deletions(-) create mode 100644 arch/powerpc/include/asm/book3s/64/kup-radix.h

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 973861421264..7371643dd8d4 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2561,6 +2561,7 @@ tsx_async_abort=off [X86] kvm.nx_huge_pages=off [X86] no_entry_flush [PPC] + no_uaccess_flush [PPC]

Exceptions: This does not have any effect on @@ -2922,6 +2923,9 @@ nospec_store_bypass_disable [HW] Disable all mitigations for the Speculative Store Bypass vulnerability

+ no_uaccess_flush + [PPC] Don't flush the L1-D cache after accessing user data. + noxsave [BUGS=X86] Disables x86 extended register state save and restore using xsave. The kernel will fallback to enabling legacy floating-point and sse state. diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h new file mode 100644 index 000000000000..aa54ac2e5659 --- /dev/null +++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h @@ -0,0 +1,22 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H +#define _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H + +DECLARE_STATIC_KEY_FALSE(uaccess_flush_key); + +/* Prototype for function defined in exceptions-64s.S */ +void do_uaccess_flush(void); + +static __always_inline void allow_user_access(void __user *to, const void __user *from, + unsigned long size) +{ +} + +static inline void prevent_user_access(void __user *to, const void __user *from, + unsigned long size) +{ + if (static_branch_unlikely(&uaccess_flush_key)) + do_uaccess_flush(); +} + +#endif /* _ASM_POWERPC_BOOK3S_64_KUP_RADIX_H */ diff --git a/arch/powerpc/include/asm/feature-fixups.h b/arch/powerpc/include/asm/feature-fixups.h index 9ad779d87b23..5bf3f0779b93 100644 --- a/arch/powerpc/include/asm/feature-fixups.h +++ b/arch/powerpc/include/asm/feature-fixups.h @@ -205,6 +205,14 @@ label##3: \ FTR_ENTRY_OFFSET 955b-956b; \ .popsection;

+#define UACCESS_FLUSH_FIXUP_SECTION \ +959: \ + .pushsection __uaccess_flush_fixup,"a"; \ + .align 2; \ +960: \ + FTR_ENTRY_OFFSET 959b-960b; \ + .popsection; + #define ENTRY_FLUSH_FIXUP_SECTION \ 957: \ .pushsection __entry_flush_fixup,"a"; \ @@ -248,6 +256,7 @@ extern long stf_barrier_fallback; extern long entry_flush_fallback; extern long __start___stf_entry_barrier_fixup, __stop___stf_entry_barrier_fixup; extern long __start___stf_exit_barrier_fixup, __stop___stf_exit_barrier_fixup; +extern long __start___uaccess_flush_fixup, __stop___uaccess_flush_fixup; extern long __start___entry_flush_fixup, __stop___entry_flush_fixup; extern long __start___rfi_flush_fixup, __stop___rfi_flush_fixup; extern long __start___barrier_nospec_fixup, __stop___barrier_nospec_fixup; diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h index 7895d5eeaf21..f0f8e36ad71f 100644 --- a/arch/powerpc/include/asm/kup.h +++ b/arch/powerpc/include/asm/kup.h @@ -6,10 +6,14 @@

#include <asm/pgtable.h>

+#ifdef CONFIG_PPC_BOOK3S_64 +#include <asm/book3s/64/kup-radix.h> +#else static inline void allow_user_access(void __user *to, const void __user *from, unsigned long size) { } static inline void prevent_user_access(void __user *to, const void __user *from, unsigned long size) { } +#endif /* CONFIG_PPC_BOOK3S_64 */

static inline void allow_read_from_user(const void __user *from, unsigned long size) { diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h index 082b56bf678d..3b45a64e491e 100644 --- a/arch/powerpc/include/asm/security_features.h +++ b/arch/powerpc/include/asm/security_features.h @@ -87,6 +87,8 @@ static inline bool security_ftr_enabled(unsigned long feature) // The L1-D cache should be flushed when entering the kernel #define SEC_FTR_L1D_FLUSH_ENTRY 0x0000000000004000ull

+// The L1-D cache should be flushed after user accesses from the kernel +#define SEC_FTR_L1D_FLUSH_UACCESS 0x0000000000008000ull

// Features enabled by default #define SEC_FTR_DEFAULT \ @@ -94,6 +96,7 @@ static inline bool security_ftr_enabled(unsigned long feature) SEC_FTR_L1D_FLUSH_PR | \ SEC_FTR_BNDS_CHK_SPEC_BAR | \ SEC_FTR_L1D_FLUSH_ENTRY | \ + SEC_FTR_L1D_FLUSH_UACCESS | \ SEC_FTR_FAVOUR_SECURITY)

#endif /* _ASM_POWERPC_SECURITY_FEATURES_H */ diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h index 556635217e5c..6f2f4497e13b 100644 --- a/arch/powerpc/include/asm/setup.h +++ b/arch/powerpc/include/asm/setup.h @@ -60,6 +60,7 @@ void setup_barrier_nospec(void); #else static inline void setup_barrier_nospec(void) { }; #endif +void do_uaccess_flush_fixups(enum l1d_flush_type types); void do_entry_flush_fixups(enum l1d_flush_type types); void do_barrier_nospec_fixups(bool enable); extern bool barrier_nospec_enabled; diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 75551690e96e..344e2758b22d 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -1529,11 +1529,8 @@ TRAMP_REAL_BEGIN(stf_barrier_fallback) .endr blr

-TRAMP_REAL_BEGIN(entry_flush_fallback) - std r9,PACA_EXRFI+EX_R9(r13) - std r10,PACA_EXRFI+EX_R10(r13) - std r11,PACA_EXRFI+EX_R11(r13) - mfctr r9 +/* Clobbers r10, r11, ctr */ +.macro L1D_DISPLACEMENT_FLUSH ld r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13) ld r11,PACA_L1D_FLUSH_SIZE(r13) srdi r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */ @@ -1559,7 +1556,14 @@ TRAMP_REAL_BEGIN(entry_flush_fallback) ld r11,(0x80 + 8)*7(r10) addi r10,r10,0x80*8 bdnz 1b +.endm

+TRAMP_REAL_BEGIN(entry_flush_fallback) + std r9,PACA_EXRFI+EX_R9(r13) + std r10,PACA_EXRFI+EX_R10(r13) + std r11,PACA_EXRFI+EX_R11(r13) + mfctr r9 + L1D_DISPLACEMENT_FLUSH mtctr r9 ld r9,PACA_EXRFI+EX_R9(r13) ld r10,PACA_EXRFI+EX_R10(r13) @@ -1575,32 +1579,7 @@ TRAMP_REAL_BEGIN(rfi_flush_fallback) std r10,PACA_EXRFI+EX_R10(r13) std r11,PACA_EXRFI+EX_R11(r13) mfctr r9 - ld r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13) - ld r11,PACA_L1D_FLUSH_SIZE(r13) - srdi r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */ - mtctr r11 - DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */ - - /* order ld/st prior to dcbt stop all streams with flushing */ - sync - - /* - * The load adresses are at staggered offsets within cachelines, - * which suits some pipelines better (on others it should not - * hurt). - */ -1: - ld r11,(0x80 + 8)*0(r10) - ld r11,(0x80 + 8)*1(r10) - ld r11,(0x80 + 8)*2(r10) - ld r11,(0x80 + 8)*3(r10) - ld r11,(0x80 + 8)*4(r10) - ld r11,(0x80 + 8)*5(r10) - ld r11,(0x80 + 8)*6(r10) - ld r11,(0x80 + 8)*7(r10) - addi r10,r10,0x80*8 - bdnz 1b - + L1D_DISPLACEMENT_FLUSH mtctr r9 ld r9,PACA_EXRFI+EX_R9(r13) ld r10,PACA_EXRFI+EX_R10(r13) @@ -1618,32 +1597,7 @@ TRAMP_REAL_BEGIN(hrfi_flush_fallback) std r10,PACA_EXRFI+EX_R10(r13) std r11,PACA_EXRFI+EX_R11(r13) mfctr r9 - ld r10,PACA_RFI_FLUSH_FALLBACK_AREA(r13) - ld r11,PACA_L1D_FLUSH_SIZE(r13) - srdi r11,r11,(7 + 3) /* 128 byte lines, unrolled 8x */ - mtctr r11 - DCBT_BOOK3S_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */ - - /* order ld/st prior to dcbt stop all streams with flushing */ - sync - - /* - * The load adresses are at staggered offsets within cachelines, - * which suits some pipelines better (on others it should not - * hurt). - */ -1: - ld r11,(0x80 + 8)*0(r10) - ld r11,(0x80 + 8)*1(r10) - ld r11,(0x80 + 8)*2(r10) - ld r11,(0x80 + 8)*3(r10) - ld r11,(0x80 + 8)*4(r10) - ld r11,(0x80 + 8)*5(r10) - ld r11,(0x80 + 8)*6(r10) - ld r11,(0x80 + 8)*7(r10) - addi r10,r10,0x80*8 - bdnz 1b - + L1D_DISPLACEMENT_FLUSH mtctr r9 ld r9,PACA_EXRFI+EX_R9(r13) ld r10,PACA_EXRFI+EX_R10(r13) @@ -1652,6 +1606,19 @@ TRAMP_REAL_BEGIN(hrfi_flush_fallback) GET_SCRATCH0(r13); hrfid

+USE_TEXT_SECTION() + +_GLOBAL(do_uaccess_flush) + UACCESS_FLUSH_FIXUP_SECTION + nop + nop + nop + blr + L1D_DISPLACEMENT_FLUSH + blr +_ASM_NOKPROBE_SYMBOL(do_uaccess_flush) +EXPORT_SYMBOL(do_uaccess_flush) + /* * Real mode exceptions actually use this too, but alternate * instruction code patches (which end up in the common .text area) diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c index 7bbd9d22d66e..122365624d3d 100644 --- a/arch/powerpc/kernel/setup_64.c +++ b/arch/powerpc/kernel/setup_64.c @@ -864,8 +864,12 @@ static enum l1d_flush_type enabled_flush_types; static void *l1d_flush_fallback_area; static bool no_rfi_flush; static bool no_entry_flush; +static bool no_uaccess_flush; bool rfi_flush; bool entry_flush; +bool uaccess_flush; +DEFINE_STATIC_KEY_FALSE(uaccess_flush_key); +EXPORT_SYMBOL(uaccess_flush_key);

static int __init handle_no_rfi_flush(char *p) { @@ -883,6 +887,14 @@ static int __init handle_no_entry_flush(char *p) } early_param("no_entry_flush", handle_no_entry_flush);

+static int __init handle_no_uaccess_flush(char *p) +{ + pr_info("uaccess-flush: disabled on command line."); + no_uaccess_flush = true; + return 0; +} +early_param("no_uaccess_flush", handle_no_uaccess_flush); + /* * The RFI flush is not KPTI, but because users will see doco that says to use * nopti we hijack that option here to also disable the RFI flush. @@ -926,6 +938,20 @@ void entry_flush_enable(bool enable) entry_flush = enable; }

+void uaccess_flush_enable(bool enable) +{ + if (enable) { + do_uaccess_flush_fixups(enabled_flush_types); + static_branch_enable(&uaccess_flush_key); + on_each_cpu(do_nothing, NULL, 1); + } else { + static_branch_disable(&uaccess_flush_key); + do_uaccess_flush_fixups(L1D_FLUSH_NONE); + } + + uaccess_flush = enable; +} + static void __ref init_fallback_flush(void) { u64 l1d_size, limit; @@ -992,6 +1018,15 @@ void setup_entry_flush(bool enable) entry_flush_enable(enable); }

+void setup_uaccess_flush(bool enable) +{ + if (cpu_mitigations_off()) + return; + + if (!no_uaccess_flush) + uaccess_flush_enable(enable); +} + #ifdef CONFIG_DEBUG_FS static int rfi_flush_set(void *data, u64 val) { @@ -1045,10 +1080,37 @@ static int entry_flush_get(void *data, u64 *val)

DEFINE_SIMPLE_ATTRIBUTE(fops_entry_flush, entry_flush_get, entry_flush_set, "%llu\n");

+static int uaccess_flush_set(void *data, u64 val) +{ + bool enable; + + if (val == 1) + enable = true; + else if (val == 0) + enable = false; + else + return -EINVAL; + + /* Only do anything if we're changing state */ + if (enable != uaccess_flush) + uaccess_flush_enable(enable); + + return 0; +} + +static int uaccess_flush_get(void *data, u64 *val) +{ + *val = uaccess_flush ? 1 : 0; + return 0; +} + +DEFINE_SIMPLE_ATTRIBUTE(fops_uaccess_flush, uaccess_flush_get, uaccess_flush_set, "%llu\n"); + static __init int rfi_flush_debugfs_init(void) { debugfs_create_file("rfi_flush", 0600, powerpc_debugfs_root, NULL, &fops_rfi_flush); debugfs_create_file("entry_flush", 0600, powerpc_debugfs_root, NULL, &fops_entry_flush); + debugfs_create_file("uaccess_flush", 0600, powerpc_debugfs_root, NULL, &fops_uaccess_flush); return 0; } device_initcall(rfi_flush_debugfs_init); diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S index 1432cf996201..695432965f20 100644 --- a/arch/powerpc/kernel/vmlinux.lds.S +++ b/arch/powerpc/kernel/vmlinux.lds.S @@ -140,6 +140,13 @@ SECTIONS __stop___stf_entry_barrier_fixup = .; }

+ . = ALIGN(8); + __uaccess_flush_fixup : AT(ADDR(__uaccess_flush_fixup) - LOAD_OFFSET) { + __start___uaccess_flush_fixup = .; + *(__uaccess_flush_fixup) + __stop___uaccess_flush_fixup = .; + } + . = ALIGN(8); __entry_flush_fixup : AT(ADDR(__entry_flush_fixup) - LOAD_OFFSET) { __start___entry_flush_fixup = .; diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c index 22bae8741cae..065a3426f0eb 100644 --- a/arch/powerpc/lib/feature-fixups.c +++ b/arch/powerpc/lib/feature-fixups.c @@ -232,6 +232,56 @@ void do_stf_barrier_fixups(enum stf_barrier_type types) do_stf_exit_barrier_fixups(types); }

+void do_uaccess_flush_fixups(enum l1d_flush_type types) +{ + unsigned int instrs[4], *dest; + long *start, *end; + int i; + + start = PTRRELOC(&__start___uaccess_flush_fixup); + end = PTRRELOC(&__stop___uaccess_flush_fixup); + + instrs[0] = 0x60000000; /* nop */ + instrs[1] = 0x60000000; /* nop */ + instrs[2] = 0x60000000; /* nop */ + instrs[3] = 0x4e800020; /* blr */ + + i = 0; + if (types == L1D_FLUSH_FALLBACK) { + instrs[3] = 0x60000000; /* nop */ + /* fallthrough to fallback flush */ + } + + if (types & L1D_FLUSH_ORI) { + instrs[i++] = 0x63ff0000; /* ori 31,31,0 speculation barrier */ + instrs[i++] = 0x63de0000; /* ori 30,30,0 L1d flush*/ + } + + if (types & L1D_FLUSH_MTTRIG) + instrs[i++] = 0x7c12dba6; /* mtspr TRIG2,r0 (SPR #882) */ + + for (i = 0; start < end; start++, i++) { + dest = (void *)start + *start; + + pr_devel("patching dest %lx\n", (unsigned long)dest); + + patch_instruction(dest, instrs[0]); + + patch_instruction((dest + 1), instrs[1]); + patch_instruction((dest + 2), instrs[2]); + patch_instruction((dest + 3), instrs[3]); + } + + printk(KERN_DEBUG "uaccess-flush: patched %d locations (%s flush)\n", i, + (types == L1D_FLUSH_NONE) ? "no" : + (types == L1D_FLUSH_FALLBACK) ? "fallback displacement" : + (types & L1D_FLUSH_ORI) ? (types & L1D_FLUSH_MTTRIG) + ? "ori+mttrig type" + : "ori type" : + (types & L1D_FLUSH_MTTRIG) ? "mttrig type" + : "unknown"); +} + void do_entry_flush_fixups(enum l1d_flush_type types) { unsigned int instrs[3], *dest; diff --git a/arch/powerpc/platforms/powernv/setup.c b/arch/powerpc/platforms/powernv/setup.c index ad51349e479b..5068dd7f6e74 100644 --- a/arch/powerpc/platforms/powernv/setup.c +++ b/arch/powerpc/platforms/powernv/setup.c @@ -127,10 +127,12 @@ static void pnv_setup_rfi_flush(void)

/* * If we are non-Power9 bare metal, we don't need to flush on kernel - * entry: it fixes a P9 specific vulnerability. + * entry or after user access: they fix a P9 specific vulnerability. */ - if (!pvr_version_is(PVR_POWER9)) + if (!pvr_version_is(PVR_POWER9)) { security_ftr_clear(SEC_FTR_L1D_FLUSH_ENTRY); + security_ftr_clear(SEC_FTR_L1D_FLUSH_UACCESS); + }

enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \ (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR) || \ @@ -142,6 +144,10 @@ static void pnv_setup_rfi_flush(void) enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY); setup_entry_flush(enable); + + enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && + security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS); + setup_uaccess_flush(enable); }

static void __init pnv_setup_arch(void) diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c index 8aa4dd87cbf2..2e0d38cafdd4 100644 --- a/arch/powerpc/platforms/pseries/setup.c +++ b/arch/powerpc/platforms/pseries/setup.c @@ -569,6 +569,10 @@ void pseries_setup_rfi_flush(void) enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && security_ftr_enabled(SEC_FTR_L1D_FLUSH_ENTRY); setup_entry_flush(enable); + + enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && + security_ftr_enabled(SEC_FTR_L1D_FLUSH_UACCESS); + setup_uaccess_flush(enable); }

#ifdef CONFIG_PCI_IOV