[PATCH] udev - safer string handling - part two

As promised, here is the next round. We provide in addition to the
already used macros:

  strfieldcpy(to, from)
  strfieldcat(to, from)

the corresponding friends, if the size of the target is not known and
must be provided by the caller:

  strnfieldcpy(to, from, maxsize)
  strnfieldcat(to, from, maxsize)

and switch nearly all possibly unsafe users of strcat(), strncat(),
strcpy() and strncpy() to these safer macros.

The last known remaining issue seems the use of sprintf() and
snprintf(). I will take on it later today or tomorrow.

diff --git a/namedev.c b/namedev.c
index 219cb8a4b84406b63f7cfcf8917eb08fcb9eee66..f688507dc39c985b389e3b1c68cf2efafce110f3 100644 (file)
--- a/namedev.c
+++ b/namedev.c
@@ -209,7 +209,9 @@ static int get_format_len(char **str)
        return -1;
 }
 
-static void apply_format(struct udevice *udev, unsigned char *string, struct sysfs_class_device *class_dev, struct sysfs_device *sysfs_device)
+static void apply_format(struct udevice *udev, char *string, size_t maxsize,
+                        struct sysfs_class_device *class_dev,
+                        struct sysfs_device *sysfs_device)
 {
        char temp[NAME_SIZE];
        char temp1[NAME_SIZE];
@@ -245,19 +247,19 @@ static void apply_format(struct udevice *udev, unsigned char *string, struct sys
                case 'b':
                        if (strlen(udev->bus_id) == 0)
                                break;
-                       strcat(pos, udev->bus_id);
+                       strnfieldcat(pos, udev->bus_id, maxsize);
                        dbg("substitute bus_id '%s'", udev->bus_id);
                        break;
                case 'k':
                        if (strlen(udev->kernel_name) == 0)
                                break;
-                       strcat(pos, udev->kernel_name);
+                       strnfieldcat(pos, udev->kernel_name, maxsize);
                        dbg("substitute kernel name '%s'", udev->kernel_name);
                        break;
                case 'n':
                        if (strlen(udev->kernel_number) == 0)
                                break;
-                       strcat(pos, udev->kernel_number);
+                       strnfieldcat(pos, udev->kernel_number, maxsize);
                        dbg("substitute kernel number '%s'", udev->kernel_number);
                                break;
                case 'm':
@@ -287,11 +289,11 @@ static void apply_format(struct udevice *udev, unsigned char *string, struct sys
                                        }
                                }
                                if (pos3) {
-                                       strcat(pos, pos3);
+                                       strnfieldcat(pos, pos3, maxsize);
                                        dbg("substitute part of result string '%s'", pos3);
                                }
                        } else {
-                               strcat(pos, udev->program_result);
+                               strnfieldcat(pos, udev->program_result, maxsize);
                                dbg("substitute result string '%s'", udev->program_result);
                        }
                        break;
@@ -302,20 +304,20 @@ static void apply_format(struct udevice *udev, unsigned char *string, struct sys
                                        dbg("sysfa attribute '%s' not found", attr);
                                        break;
                                }
-                               strcpy(pos, tmpattr->value);
+                               strnfieldcpy(pos, tmpattr->value, maxsize);
                                dbg("substitute sysfs value '%s'", tmpattr->value);
                        } else {
                                dbg("missing attribute");
                        }
                        break;
                case '%':
-                       strcat(pos, "%");
+                       strnfieldcat(pos, "%", maxsize);
                        break;
                default:
                        dbg("unknown substitution type '%%%c'", c);
                        break;
                }
-               strcat(pos, tail);
+               strnfieldcat(pos, tail, maxsize);
        }
 }
 
@@ -462,7 +464,7 @@ static int execute_program(char *path, char *value, int len)
                                strncpy(value, buffer, len);
                                pos = value + strlen(value)-1;
                                if (pos[0] == '\n')
-                               pos[0] = '\0';
+                                       pos[0] = '\0';
                                dbg("result is '%s'", value);
                        }
                }
@@ -733,7 +735,8 @@ static int match_rule(struct config_device *dev, struct sysfs_class_device *clas
                /* execute external program */
                if (dev->program[0] != '\0') {
                        dbg("check " FIELD_PROGRAM);
-                       apply_format(udev, dev->program, class_dev, sysfs_device);
+                       apply_format(udev, dev->program, sizeof(dev->program),
+                                    class_dev, sysfs_device);
                        if (execute_program(dev->program, udev->program_result, NAME_SIZE) != 0) {
                                dbg(FIELD_PROGRAM " returned nozero");
                                goto try_parent;
@@ -825,8 +828,10 @@ int namedev_name_device(struct sysfs_class_device *class_dev, struct udevice *ud
 
 found:
        /* substitute placeholder */
-       apply_format(udev, udev->name, class_dev, sysfs_device);
-       apply_format(udev, udev->symlink, class_dev, sysfs_device);
+       apply_format(udev, udev->name, sizeof(udev->name),
+                    class_dev, sysfs_device);
+       apply_format(udev, udev->symlink, sizeof(udev->symlink),
+                    class_dev, sysfs_device);
        udev->partitions = dev->partitions;
 done:
        perm = find_perm(udev->name);

diff --git a/udev.h b/udev.h
index fc44a9847c09f71e4a83e9401be9b9b9f0edbb77..0ce010f3c49071131795f70a0873c02fba3d9428 100644 (file)
--- a/udev.h
+++ b/udev.h
@@ -64,7 +64,19 @@ do { \
 #define strfieldcat(to, from) \
 do { \
        to[sizeof(to)-1] = '\0'; \
-       strncat(to, from, sizeof(to) - strlen(to) -1); \
+       strncat(to, from, sizeof(to) - strlen(to)-1); \
+} while (0)
+
+#define strnfieldcpy(to, from, maxsize) \
+do { \
+       to[maxsize-1] = '\0'; \
+       strncpy(to, from, maxsize-1); \
+} while (0)
+
+#define strnfieldcat(to, from, maxsize) \
+do { \
+       to[maxsize-1] = '\0'; \
+       strncat(to, from, maxsize - strlen(to)-1); \
 } while (0)
 
 extern int udev_add_device(char *path, char *subsystem, int fake);

diff --git a/udev_config.c b/udev_config.c
index cade81cf207ccf3e1e9bbc454b8cce24a2629d9e..de83ef9c4c770160ae52645695fe09bec2379686 100644 (file)
--- a/udev_config.c
+++ b/udev_config.c
@@ -81,7 +81,7 @@ static void init_variables(void)
 #define set_var(_name, _var)                           \
        if (strcasecmp(variable, _name) == 0) {         \
                dbg_parse("%s = '%s'", _name, value);   \
-               strncpy(_var, value, sizeof(_var));     \
+               strnfieldcpy(_var, value, sizeof(_var));\
        }
 
 #define set_bool(_name, _var)                          \