fs/kernel_read_file: Switch buffer size arg to size_t

In preparation for further refactoring of kernel_read_file*(), rename
the "max_size" argument to the more accurate "buf_size", and correct
its type to size_t. Add kerndoc to explain the specifics of how the
arguments will be used. Note that with buf_size now size_t, it can no
longer be negative (and was never called with a negative value). Adjust
callers to use it as a "maximum size" when *buf is NULL.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Acked-by: Scott Branden <scott.branden@broadcom.com>
Link: https://lore.kernel.org/r/20201002173828.2099543-7-keescook@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/kernel_read_file.c b/fs/kernel_read_file.c
index dc28a8d..e21a760 100644 (file)
--- a/fs/kernel_read_file.c
+++ b/fs/kernel_read_file.c
@@ -5,15 +5,31 @@
 #include <linux/security.h>
 #include <linux/vmalloc.h>
 
+/**
+ * kernel_read_file() - read file contents into a kernel buffer
+ *
+ * @file       file to read from
+ * @buf                pointer to a "void *" buffer for reading into (if
+ *             *@buf is NULL, a buffer will be allocated, and
+ *             @buf_size will be ignored)
+ * @buf_size   size of buf, if already allocated. If @buf not
+ *             allocated, this is the largest size to allocate.
+ * @id         the kernel_read_file_id identifying the type of
+ *             file contents being read (for LSMs to examine)
+ *
+ * Returns number of bytes read (no single read will be bigger
+ * than INT_MAX), or negative on error.
+ *
+ */
 int kernel_read_file(struct file *file, void **buf,
-                    loff_t max_size, enum kernel_read_file_id id)
+                    size_t buf_size, enum kernel_read_file_id id)
 {
        loff_t i_size, pos;
        ssize_t bytes = 0;
        void *allocated = NULL;
        int ret;
 
-       if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
+       if (!S_ISREG(file_inode(file)->i_mode))
                return -EINVAL;
 
        ret = deny_write_access(file);
@@ -29,7 +45,7 @@ int kernel_read_file(struct file *file, void **buf,
                ret = -EINVAL;
                goto out;
        }
-       if (i_size > INT_MAX || (max_size > 0 && i_size > max_size)) {
+       if (i_size > INT_MAX || i_size > buf_size) {
                ret = -EFBIG;
                goto out;
        }
@@ -75,7 +91,7 @@ out:
 EXPORT_SYMBOL_GPL(kernel_read_file);
 
 int kernel_read_file_from_path(const char *path, void **buf,
-                              loff_t max_size, enum kernel_read_file_id id)
+                              size_t buf_size, enum kernel_read_file_id id)
 {
        struct file *file;
        int ret;
@@ -87,14 +103,14 @@ int kernel_read_file_from_path(const char *path, void **buf,
        if (IS_ERR(file))
                return PTR_ERR(file);
 
-       ret = kernel_read_file(file, buf, max_size, id);
+       ret = kernel_read_file(file, buf, buf_size, id);
        fput(file);
        return ret;
 }
 EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
 
 int kernel_read_file_from_path_initns(const char *path, void **buf,
-                                     loff_t max_size,
+                                     size_t buf_size,
                                      enum kernel_read_file_id id)
 {
        struct file *file;
@@ -113,13 +129,13 @@ int kernel_read_file_from_path_initns(const char *path, void **buf,
        if (IS_ERR(file))
                return PTR_ERR(file);
 
-       ret = kernel_read_file(file, buf, max_size, id);
+       ret = kernel_read_file(file, buf, buf_size, id);
        fput(file);
        return ret;
 }
 EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
 
-int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
+int kernel_read_file_from_fd(int fd, void **buf, size_t buf_size,
                             enum kernel_read_file_id id)
 {
        struct fd f = fdget(fd);
@@ -128,7 +144,7 @@ int kernel_read_file_from_fd(int fd, void **buf, loff_t max_size,
        if (!f.file)
                goto out;
 
-       ret = kernel_read_file(f.file, buf, max_size, id);
+       ret = kernel_read_file(f.file, buf, buf_size, id);
 out:
        fdput(f);
        return ret;

diff --git a/include/linux/kernel_read_file.h b/include/linux/kernel_read_file.h
index 0ca0bdb..910039e 100644 (file)
--- a/include/linux/kernel_read_file.h
+++ b/include/linux/kernel_read_file.h
@@ -36,16 +36,16 @@ static inline const char *kernel_read_file_id_str(enum kernel_read_file_id id)
 }
 
 int kernel_read_file(struct file *file,
-                    void **buf, loff_t max_size,
+                    void **buf, size_t buf_size,
                     enum kernel_read_file_id id);
 int kernel_read_file_from_path(const char *path,
-                              void **buf, loff_t max_size,
+                              void **buf, size_t buf_size,
                               enum kernel_read_file_id id);
 int kernel_read_file_from_path_initns(const char *path,
-                                     void **buf, loff_t max_size,
+                                     void **buf, size_t buf_size,
                                      enum kernel_read_file_id id);
 int kernel_read_file_from_fd(int fd,
-                            void **buf, loff_t max_size,
+                            void **buf, size_t buf_size,
                             enum kernel_read_file_id id);
 
 #endif /* _LINUX_KERNEL_READ_FILE_H */

diff --git a/security/integrity/digsig.c b/security/integrity/digsig.c
index 97661ff..04f779c 100644 (file)
--- a/security/integrity/digsig.c
+++ b/security/integrity/digsig.c
@@ -175,7 +175,7 @@ int __init integrity_load_x509(const unsigned int id, const char *path)
        int rc;
        key_perm_t perm;
 
-       rc = kernel_read_file_from_path(path, &data, 0,
+       rc = kernel_read_file_from_path(path, &data, INT_MAX,
                                        READING_X509_CERTIFICATE);
        if (rc < 0) {
                pr_err("Unable to open file: %s (%d)", path, rc);

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index 602f527..692b83e 100644 (file)
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -284,7 +284,7 @@ static ssize_t ima_read_policy(char *path)
        datap = path;
        strsep(&datap, "\n");
 
-       rc = kernel_read_file_from_path(path, &data, 0, READING_POLICY);
+       rc = kernel_read_file_from_path(path, &data, INT_MAX, READING_POLICY);
        if (rc < 0) {
                pr_err("Unable to open file: %s (%d)", path, rc);
                return rc;