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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/include/asm/futex.h | 4 +++ arch/powerpc/include/asm/kup.h | 36 ++++++++++++++++++++++++++++++++ arch/powerpc/include/asm/uaccess.h | 39 ++++++++++++++++++++++++++--------- arch/powerpc/lib/checksum_wrappers.c | 4 +++ 4 files changed, 74 insertions(+), 9 deletions(-) create mode 100644 arch/powerpc/include/asm/kup.h
--- a/arch/powerpc/include/asm/futex.h +++ b/arch/powerpc/include/asm/futex.h @@ -36,6 +36,7 @@ static inline int arch_futex_atomic_op_i { int oldval = 0, ret;
+ allow_write_to_user(uaddr, sizeof(*uaddr)); pagefault_disable();
switch (op) { @@ -62,6 +63,7 @@ static inline int arch_futex_atomic_op_i
*oval = oldval;
+ prevent_write_to_user(uaddr, sizeof(*uaddr)); return ret; }
@@ -75,6 +77,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, 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\ @@ -97,6 +100,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, : "cc", "memory");
*uval = prev; + prevent_write_to_user(uaddr, sizeof(*uaddr)); return ret; }
--- /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_ */ --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -9,6 +9,7 @@ #include <asm/asm-compat.h> #include <asm/processor.h> #include <asm/page.h> +#include <asm/kup.h>
#define VERIFY_READ 0 #define VERIFY_WRITE 1 @@ -164,6 +165,7 @@ 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; \ @@ -171,6 +173,7 @@ 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) \ @@ -252,6 +255,7 @@ 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; \ @@ -259,6 +263,7 @@ do { \ case 8: __get_user_asm2(x, ptr, retval); break; \ default: (x) = __get_user_bad(); \ } \ + prevent_read_from_user(ptr, size); \ } while (0)
#define __get_user_nocheck(x, ptr, size) \ @@ -312,9 +317,14 @@ extern unsigned long __copy_tofrom_user( static inline unsigned long copy_from_user(void *to, const void __user *from, unsigned long n) { + unsigned long ret; + if (likely(access_ok(VERIFY_READ, from, n))) { check_object_size(to, n, false); - return __copy_tofrom_user((__force void __user *)to, from, n); + allow_user_access(to, from, n); + ret = __copy_tofrom_user((__force void __user *)to, from, n); + prevent_user_access(to, from, n); + return ret; } memset(to, 0, n); return n; @@ -347,8 +357,9 @@ extern unsigned long copy_in_user(void _ static inline unsigned long __copy_from_user_inatomic(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: @@ -375,14 +386,18 @@ static inline unsigned long __copy_from_ check_object_size(to, n, false);
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 __copy_to_user_inatomic(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: @@ -403,8 +418,10 @@ static inline unsigned long __copy_to_us }
check_object_size(from, n, true); - - 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; }
static inline unsigned long __copy_from_user(void *to, @@ -425,10 +442,14 @@ extern unsigned long __clear_user(void _
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); --- 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 voi 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 voi }
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 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 }
out: + prevent_write_to_user(dst, len); return (__force __wsum)csum; } EXPORT_SYMBOL(csum_and_copy_to_user);