Add error injection with wrong storage capacity

Closes #62

README.md

@@ -14,6 +14,13 @@ Supported fault injections are:
   but applicable to any file operation).
 - `errinj_slowdown` - slowdown invoked file operation.
 - `errinj_1byte_read` - amount of data `read()` is returned is limited by 1 byte.
+- `errinj_wrong_capacity` - report a wrong storage capacity. There are many
+  fraudulent USB sticks in circulation that report to have a high capacity (ex:
+  8GB) but are really only capable of storing a much smaller amount (ex: 1GB).
+  Attempts to write on these devices will often result in unrelated files being
+  overwritten. Any use of a fraudulent flash memory device can easily lead to
+  database corruption, therefore.
+  https://www.sqlite.org/howtocorrupt.html
 
 ### Building
 

unreliablefs.conf.5

@@ -38,6 +38,8 @@ limited by supported errno's.
 File operation slowdown for nanoseconds specified by duration parameter.
 .It Cm errinj_1byte_read
 Return exactly 1 byte on every read() operation.
+.It Cm errinj_wrong_capacity
+Report a wrong storage capacity.
 .El
 .Pp
 The options are:

unreliablefs_errinj.c

@@ -22,6 +22,7 @@ const char *errinj_name[] =
     "errinj_noop",
     "errinj_slowdown",
     "errinj_1byte_read",
+    "errinj_wrong_capacity",
 };
 
 typedef enum {
@@ -30,6 +31,7 @@ typedef enum {
     ERRINJ_NOOP,
     ERRINJ_SLOWDOWN,
     ERRINJ_1BYTE_READ,
+    ERRINJ_WRONG_CAPACITY,
 } errinj_type;
 
 typedef struct errinj_conf errinj_conf;

unreliablefs_errinj.h

@@ -25,6 +25,7 @@
 
 #define ERRNO_NOOP -999
 #define ERRNO_1BYTE_READ -998
+#define ERRNO_WRONG_CAPACITY -997
 
 int error_inject(const char* path, fuse_op operation);
 struct err_inj_q *config_init(const char* conf_path);

unreliablefs_ops.c

@@ -386,6 +386,8 @@ int unreliable_statfs(const char *path, struct statvfs *buf)
     int ret = error_inject(path, OP_STATFS);
     if (ret == -ERRNO_NOOP) {
         return 0;
+    if (ret == -ERRNO_WRONG_CAPACITY) {
+        /* wrong capacity */
     } else if (ret) {
         return ret;
     }