Merge tag 'usercopy-v4.8-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees...

Pull usercopy hardening fix from Kees Cook:
 "Expand the arm64 vmalloc check to include skipping the module space
  too"

* tag 'usercopy-v4.8-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  mm: usercopy: Check for module addresses

diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index a939f5e..5c89a07 100644 (file)
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -430,6 +430,7 @@ static void elf_kcore_store_hdr(char *bufp, int nphdr, int dataoff)
 static ssize_t
 read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
 {
+       char *buf = file->private_data;
        ssize_t acc = 0;
        size_t size, tsz;
        size_t elf_buflen;
@@ -500,23 +501,20 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
                        if (clear_user(buffer, tsz))
                                return -EFAULT;
                } else if (is_vmalloc_or_module_addr((void *)start)) {
-                       char * elf_buf;
-
-                       elf_buf = kzalloc(tsz, GFP_KERNEL);
-                       if (!elf_buf)
-                               return -ENOMEM;
-                       vread(elf_buf, (char *)start, tsz);
+                       vread(buf, (char *)start, tsz);
                        /* we have to zero-fill user buffer even if no read */
-                       if (copy_to_user(buffer, elf_buf, tsz)) {
-                               kfree(elf_buf);
+                       if (copy_to_user(buffer, buf, tsz))
                                return -EFAULT;
-                       }
-                       kfree(elf_buf);
                } else {
                        if (kern_addr_valid(start)) {
                                unsigned long n;
 
-                               n = copy_to_user(buffer, (char *)start, tsz);
+                               /*
+                                * Using bounce buffer to bypass the
+                                * hardened user copy kernel text checks.
+                                */
+                               memcpy(buf, (char *) start, tsz);
+                               n = copy_to_user(buffer, buf, tsz);
                                /*
                                 * We cannot distinguish between fault on source
                                 * and fault on destination. When this happens
@@ -549,6 +547,11 @@ static int open_kcore(struct inode *inode, struct file *filp)
 {
        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;
+
+       filp->private_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
+       if (!filp->private_data)
+               return -ENOMEM;
+
        if (kcore_need_update)
                kcore_update_ram();
        if (i_size_read(inode) != proc_root_kcore->size) {
@@ -559,10 +562,16 @@ static int open_kcore(struct inode *inode, struct file *filp)
        return 0;
 }
 
+static int release_kcore(struct inode *inode, struct file *file)
+{
+       kfree(file->private_data);
+       return 0;
+}
 
 static const struct file_operations proc_kcore_operations = {
        .read           = read_kcore,
        .open           = open_kcore,
+       .release        = release_kcore,
        .llseek         = default_llseek,
 };
 

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 66a1260..7e3d537 100644 (file)
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -571,56 +571,56 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size)
  */
 static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
 {
-       int ret = 0;
        char __user *end = uaddr + size - 1;
 
        if (unlikely(size == 0))
-               return ret;
+               return 0;
 
+       if (unlikely(uaddr > end))
+               return -EFAULT;
        /*
         * Writing zeroes into userspace here is OK, because we know that if
         * the zero gets there, we'll be overwriting it.
         */
-       while (uaddr <= end) {
-               ret = __put_user(0, uaddr);
-               if (ret != 0)
-                       return ret;
+       do {
+               if (unlikely(__put_user(0, uaddr) != 0))
+                       return -EFAULT;
                uaddr += PAGE_SIZE;
-       }
+       } while (uaddr <= end);
 
        /* Check whether the range spilled into the next page. */
        if (((unsigned long)uaddr & PAGE_MASK) ==
                        ((unsigned long)end & PAGE_MASK))
-               ret = __put_user(0, end);
+               return __put_user(0, end);
 
-       return ret;
+       return 0;
 }
 
 static inline int fault_in_multipages_readable(const char __user *uaddr,
                                               int size)
 {
        volatile char c;
-       int ret = 0;
        const char __user *end = uaddr + size - 1;
 
        if (unlikely(size == 0))
-               return ret;
+               return 0;
 
-       while (uaddr <= end) {
-               ret = __get_user(c, uaddr);
-               if (ret != 0)
-                       return ret;
+       if (unlikely(uaddr > end))
+               return -EFAULT;
+
+       do {
+               if (unlikely(__get_user(c, uaddr) != 0))
+                       return -EFAULT;
                uaddr += PAGE_SIZE;
-       }
+       } while (uaddr <= end);
 
        /* Check whether the range spilled into the next page. */
        if (((unsigned long)uaddr & PAGE_MASK) ==
                        ((unsigned long)end & PAGE_MASK)) {
-               ret = __get_user(c, end);
-               (void)c;
+               return __get_user(c, end);
        }
 
-       return ret;
+       return 0;
 }
 
 int add_to_page_cache_locked(struct page *page, struct address_space *mapping,