10 files changed, 169 insertions, 68 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f2ee6a8ffe65..1fe24b624d44 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -62,6 +62,7 @@ config X86
         select ARCH_HAS_PMEM_API                if X86_64
         select ARCH_HAS_REFCOUNT
         select ARCH_HAS_UACCESS_FLUSHCACHE      if X86_64
+        select ARCH_HAS_UACCESS_MCSAFE          if X86_64
         select ARCH_HAS_SET_MEMORY
         select ARCH_HAS_SG_CHAIN
         select ARCH_HAS_STRICT_KERNEL_RWX
diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h
index 533f74c300c2..d33f92b9fa22 100644
--- a/arch/x86/include/asm/string_64.h
+++ b/arch/x86/include/asm/string_64.h
@@ -116,7 +116,8 @@ int strcmp(const char *cs, const char *ct);
 #endif
 
 #define __HAVE_ARCH_MEMCPY_MCSAFE 1
-__must_check int memcpy_mcsafe_unrolled(void *dst, const void *src, size_t cnt);
+__must_check unsigned long __memcpy_mcsafe(void *dst, const void *src,
+                size_t cnt);
 DECLARE_STATIC_KEY_FALSE(mcsafe_key);
 
 /**
@@ -131,14 +132,15 @@ DECLARE_STATIC_KEY_FALSE(mcsafe_key);
  * actually do machine check recovery. Everyone else can just
  * use memcpy().
  *
- * Return 0 for success, -EFAULT for fail
+ * Return 0 for success, or number of bytes not copied if there was an
+ * exception.
  */
-static __always_inline __must_check int
+static __always_inline __must_check unsigned long
 memcpy_mcsafe(void *dst, const void *src, size_t cnt)
 {
 #ifdef CONFIG_X86_MCE
         if (static_branch_unlikely(&mcsafe_key))
-                return memcpy_mcsafe_unrolled(dst, src, cnt);
+                return __memcpy_mcsafe(dst, src, cnt);
         else
 #endif
                 memcpy(dst, src, cnt);
diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 62546b3a398e..62acb613114b 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -47,6 +47,17 @@ copy_user_generic(void *to, const void *from, unsigned len)
 }
 
 static __always_inline __must_check unsigned long
+copy_to_user_mcsafe(void *to, const void *from, unsigned len)
+{
+        unsigned long ret;
+
+        __uaccess_begin();
+        ret = memcpy_mcsafe(to, from, len);
+        __uaccess_end();
+        return ret;
+}
+
+static __always_inline __must_check unsigned long
 raw_copy_from_user(void *dst, const void __user *src, unsigned long size)
 {
         int ret = 0;
@@ -194,4 +205,7 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
 unsigned long
 copy_user_handle_tail(char *to, char *from, unsigned len);
 
+unsigned long
+mcsafe_handle_tail(char *to, char *from, unsigned len);
+
 #endif /* _ASM_X86_UACCESS_64_H */
diff --git a/arch/x86/lib/memcpy_64.S b/arch/x86/lib/memcpy_64.S
index 9a53a06e5a3e..c3b527a9f95d 100644
--- a/arch/x86/lib/memcpy_64.S
+++ b/arch/x86/lib/memcpy_64.S
@@ -184,11 +184,11 @@ ENDPROC(memcpy_orig)
 
 #ifndef CONFIG_UML
 /*
- * memcpy_mcsafe_unrolled - memory copy with machine check exception handling
+ * __memcpy_mcsafe - memory copy with machine check exception handling
  * Note that we only catch machine checks when reading the source addresses.
  * Writes to target are posted and don't generate machine checks.
  */
-ENTRY(memcpy_mcsafe_unrolled)
+ENTRY(__memcpy_mcsafe)
         cmpl $8, %edx
         /* Less than 8 bytes? Go to byte copy loop */
         jb .L_no_whole_words
@@ -204,58 +204,29 @@ ENTRY(memcpy_mcsafe_unrolled)
         subl $8, %ecx
         negl %ecx
         subl %ecx, %edx
-.L_copy_leading_bytes:
+.L_read_leading_bytes:
         movb (%rsi), %al
+.L_write_leading_bytes:
         movb %al, (%rdi)
         incq %rsi
         incq %rdi
         decl %ecx
-        jnz .L_copy_leading_bytes
+        jnz .L_read_leading_bytes
 
 .L_8byte_aligned:
-        /* Figure out how many whole cache lines (64-bytes) to copy */
-        movl %edx, %ecx
-        andl $63, %edx
-        shrl $6, %ecx
-        jz .L_no_whole_cache_lines
-
-        /* Loop copying whole cache lines */
-.L_cache_w0: movq (%rsi), %r8
-.L_cache_w1: movq 1*8(%rsi), %r9
-.L_cache_w2: movq 2*8(%rsi), %r10
-.L_cache_w3: movq 3*8(%rsi), %r11
-        movq %r8, (%rdi)
-        movq %r9, 1*8(%rdi)
-        movq %r10, 2*8(%rdi)
-        movq %r11, 3*8(%rdi)
-.L_cache_w4: movq 4*8(%rsi), %r8
-.L_cache_w5: movq 5*8(%rsi), %r9
-.L_cache_w6: movq 6*8(%rsi), %r10
-.L_cache_w7: movq 7*8(%rsi), %r11
-        movq %r8, 4*8(%rdi)
-        movq %r9, 5*8(%rdi)
-        movq %r10, 6*8(%rdi)
-        movq %r11, 7*8(%rdi)
-        leaq 64(%rsi), %rsi
-        leaq 64(%rdi), %rdi
-        decl %ecx
-        jnz .L_cache_w0
-
-        /* Are there any trailing 8-byte words? */
-.L_no_whole_cache_lines:
         movl %edx, %ecx
         andl $7, %edx
         shrl $3, %ecx
         jz .L_no_whole_words
 
-        /* Copy trailing words */
-.L_copy_trailing_words:
+.L_read_words:
         movq (%rsi), %r8
-        mov %r8, (%rdi)
-        leaq 8(%rsi), %rsi
-        leaq 8(%rdi), %rdi
+.L_write_words:
+        movq %r8, (%rdi)
+        addq $8, %rsi
+        addq $8, %rdi
         decl %ecx
-        jnz .L_copy_trailing_words
+        jnz .L_read_words
 
         /* Any trailing bytes? */
 .L_no_whole_words:
@@ -264,38 +235,53 @@ ENTRY(memcpy_mcsafe_unrolled)
 
         /* Copy trailing bytes */
         movl %edx, %ecx
-.L_copy_trailing_bytes:
+.L_read_trailing_bytes:
         movb (%rsi), %al
+.L_write_trailing_bytes:
         movb %al, (%rdi)
         incq %rsi
         incq %rdi
         decl %ecx
-        jnz .L_copy_trailing_bytes
+        jnz .L_read_trailing_bytes
 
         /* Copy successful. Return zero */
 .L_done_memcpy_trap:
         xorq %rax, %rax
         ret
-ENDPROC(memcpy_mcsafe_unrolled)
-EXPORT_SYMBOL_GPL(memcpy_mcsafe_unrolled)
+ENDPROC(__memcpy_mcsafe)
+EXPORT_SYMBOL_GPL(__memcpy_mcsafe)
 
         .section .fixup, "ax"
-        /* Return -EFAULT for any failure */
-.L_memcpy_mcsafe_fail:
-        mov     $-EFAULT, %rax
+        /*
+         * Return number of bytes not copied for any failure. Note that
+         * there is no "tail" handling since the source buffer is 8-byte
+         * aligned and poison is cacheline aligned.
+         */
+.E_read_words:
+        shll    $3, %ecx
+.E_leading_bytes:
+        addl    %edx, %ecx
+.E_trailing_bytes:
+        mov     %ecx, %eax
         ret
 
+        /*
+         * For write fault handling, given the destination is unaligned,
+         * we handle faults on multi-byte writes with a byte-by-byte
+         * copy up to the write-protected page.
+         */
+.E_write_words:
+        shll    $3, %ecx
+        addl    %edx, %ecx
+        movl    %ecx, %edx
+        jmp mcsafe_handle_tail
+
         .previous
 
-        _ASM_EXTABLE_FAULT(.L_copy_leading_bytes, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w0, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w1, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w2, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w3, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w4, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w5, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w6, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_cache_w7, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_copy_trailing_words, .L_memcpy_mcsafe_fail)
-        _ASM_EXTABLE_FAULT(.L_copy_trailing_bytes, .L_memcpy_mcsafe_fail)
+        _ASM_EXTABLE_FAULT(.L_read_leading_bytes, .E_leading_bytes)
+        _ASM_EXTABLE_FAULT(.L_read_words, .E_read_words)
+        _ASM_EXTABLE_FAULT(.L_read_trailing_bytes, .E_trailing_bytes)
+        _ASM_EXTABLE(.L_write_leading_bytes, .E_leading_bytes)
+        _ASM_EXTABLE(.L_write_words, .E_write_words)
+        _ASM_EXTABLE(.L_write_trailing_bytes, .E_trailing_bytes)
 #endif
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index a624dcc4de10..9c5606d88f61 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -74,6 +74,27 @@ copy_user_handle_tail(char *to, char *from, unsigned len)
         return len;
 }
 
+/*
+ * Similar to copy_user_handle_tail, probe for the write fault point,
+ * but reuse __memcpy_mcsafe in case a new read error is encountered.
+ * clac() is handled in _copy_to_iter_mcsafe().
+ */
+__visible unsigned long
+mcsafe_handle_tail(char *to, char *from, unsigned len)
+{
+        for (; len; --len, to++, from++) {
+                /*
+                 * Call the assembly routine back directly since
+                 * memcpy_mcsafe() may silently fallback to memcpy.
+                 */
+                unsigned long rem = __memcpy_mcsafe(to, from, 1);
+
+                if (rem)
+                        break;
+        }
+        return len;
+}
+
 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 /**
  * clean_cache_range - write back a cache range with CLWB
diff --git a/drivers/nvdimm/claim.c b/drivers/nvdimm/claim.c
index 30852270484f..2e96b34bc936 100644
--- a/drivers/nvdimm/claim.c
+++ b/drivers/nvdimm/claim.c
@@ -276,7 +276,8 @@ static int nsio_rw_bytes(struct nd_namespace_common *ndns,
         if (rw == READ) {
                 if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align)))
                         return -EIO;
-                return memcpy_mcsafe(buf, nsio->addr + offset, size);
+                if (memcpy_mcsafe(buf, nsio->addr + offset, size) != 0)
+                        return -EIO;
         }
 
         if (unlikely(is_bad_pmem(&nsio->bb, sector, sz_align))) {
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 9d714926ecf5..e023d6aa22b5 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -101,15 +101,15 @@ static blk_status_t read_pmem(struct page *page, unsigned int off,
                 void *pmem_addr, unsigned int len)
 {
         unsigned int chunk;
-        int rc;
+        unsigned long rem;
         void *mem;
 
         while (len) {
                 mem = kmap_atomic(page);
                 chunk = min_t(unsigned int, len, PAGE_SIZE);
-                rc = memcpy_mcsafe(mem + off, pmem_addr, chunk);
+                rem = memcpy_mcsafe(mem + off, pmem_addr, chunk);
                 kunmap_atomic(mem);
-                if (rc)
+                if (rem)
                         return BLK_STS_IOERR;
                 len -= chunk;
                 off = 0;
diff --git a/include/linux/string.h b/include/linux/string.h
index dd39a690c841..4a5a0eb7df51 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -147,8 +147,8 @@ extern int memcmp(const void *,const void *,__kernel_size_t);
 extern void * memchr(const void *,int,__kernel_size_t);
 #endif
 #ifndef __HAVE_ARCH_MEMCPY_MCSAFE
-static inline __must_check int memcpy_mcsafe(void *dst, const void *src,
-                size_t cnt)
+static inline __must_check unsigned long memcpy_mcsafe(void *dst,
+                const void *src, size_t cnt)
 {
         memcpy(dst, src, cnt);
         return 0;
diff --git a/include/linux/uio.h b/include/linux/uio.h
index e67e12adb136..f5766e853a77 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -154,6 +154,12 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 #define _copy_from_iter_flushcache _copy_from_iter_nocache
 #endif
 
+#ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE
+size_t _copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i);
+#else
+#define _copy_to_iter_mcsafe _copy_to_iter
+#endif
+
 static __always_inline __must_check
 size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 {
@@ -163,6 +169,15 @@ size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
                 return _copy_from_iter_flushcache(addr, bytes, i);
 }
 
+static __always_inline __must_check
+size_t copy_to_iter_mcsafe(void *addr, size_t bytes, struct iov_iter *i)
+{
+        if (unlikely(!check_copy_size(addr, bytes, false)))
+                return 0;
+        else
+                return _copy_to_iter_mcsafe(addr, bytes, i);
+}
+
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index fdae394172fa..7e43cd54c84c 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -573,6 +573,67 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 }
 EXPORT_SYMBOL(_copy_to_iter);
 
+#ifdef CONFIG_ARCH_HAS_UACCESS_MCSAFE
+static int copyout_mcsafe(void __user *to, const void *from, size_t n)
+{
+        if (access_ok(VERIFY_WRITE, to, n)) {
+                kasan_check_read(from, n);
+                n = copy_to_user_mcsafe((__force void *) to, from, n);
+        }
+        return n;
+}
+
+static unsigned long memcpy_mcsafe_to_page(struct page *page, size_t offset,
+                const char *from, size_t len)
+{
+        unsigned long ret;
+        char *to;
+
+        to = kmap_atomic(page);
+        ret = memcpy_mcsafe(to + offset, from, len);
+        kunmap_atomic(to);
+
+        return ret;
+}
+
+size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i)
+{
+        const char *from = addr;
+        unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
+
+        if (unlikely(i->type & ITER_PIPE)) {
+                WARN_ON(1);
+                return 0;
+        }
+        if (iter_is_iovec(i))
+                might_fault();
+        iterate_and_advance(i, bytes, v,
+                copyout_mcsafe(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
+                ({
+                rem = memcpy_mcsafe_to_page(v.bv_page, v.bv_offset,
+                               (from += v.bv_len) - v.bv_len, v.bv_len);
+                if (rem) {
+                        curr_addr = (unsigned long) from;
+                        bytes = curr_addr - s_addr - rem;
+                        return bytes;
+                }
+                }),
+                ({
+                rem = memcpy_mcsafe(v.iov_base, (from += v.iov_len) - v.iov_len,
+                                v.iov_len);
+                if (rem) {
+                        curr_addr = (unsigned long) from;
+                        bytes = curr_addr - s_addr - rem;
+                        return bytes;
+                }
+                })
+        )
+
+        return bytes;
+}
+EXPORT_SYMBOL_GPL(_copy_to_iter_mcsafe);
+#endif /* CONFIG_ARCH_HAS_UACCESS_MCSAFE */
+
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 {
         char *to = addr;