Merge pull request #1682 from hMcLauchlan/inject-qol

QoL improvements for inject

tools/inject.py

@@ -33,6 +33,7 @@
 # 16-Mar-2018   Howard McLauchlan   Created this.
 
 import argparse
+import re
 from bcc import BPF
 
 
@@ -294,6 +295,21 @@ class Probe:
 
 
 class Tool:
+
+    examples ="""
+EXAMPLES:
+# ./inject.py kmalloc -v 'SyS_mount()'
+    Fails all calls to syscall mount
+# ./inject.py kmalloc -v '(true) => SyS_mount()(true)'
+    Explicit rewriting of above
+# ./inject.py kmalloc -v 'mount_subtree() => btrfs_mount()'
+    Fails btrfs mounts only
+# ./inject.py kmalloc -v 'd_alloc_parallel(struct dentry *parent, const struct \\
+    qstr *name)(STRCMP(name->name, 'bananas'))'
+    Fails dentry allocations of files named 'bananas'
+# ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
+    Fails calls to syscall mount with 1% probability
+    """
     # add cases as necessary
     error_injection_mapping = {
         "kmalloc": "should_failslab(struct kmem_cache *s, gfp_t gfpflags)",
@@ -303,8 +319,9 @@ class Tool:
     def __init__(self):
         parser = argparse.ArgumentParser(description="Fail specified kernel" +
                 " functionality when call chain and predicates are met",
-                formatter_class=argparse.RawDescriptionHelpFormatter)
-        parser.add_argument(metavar="mode", dest="mode",
+                formatter_class=argparse.RawDescriptionHelpFormatter,
+                epilog=Tool.examples)
+        parser.add_argument(dest="mode", choices=['kmalloc','bio'],
                 help="indicate which base kernel function to fail")
         parser.add_argument(metavar="spec", dest="spec",
                 help="specify call chain")
@@ -315,7 +332,7 @@ class Tool:
                 metavar="probability", type=float,
                 help="probability that this call chain will fail")
         parser.add_argument("-v", "--verbose", action="store_true",
-            help="print BPF program")
+                help="print BPF program")
         self.args = parser.parse_args()
 
         self.program = ""
@@ -350,6 +367,7 @@ class Tool:
         frames = []
         cur_frame = []
         i = 0
+        last_frame_added = 0
 
         while i < len(data):
             # improper input
@@ -360,6 +378,10 @@ class Tool:
             count -= c == ')'
             if not count:
                 if c == '\0' or (c == '=' and data[i + 1] == '>'):
+                    # This block is closing a chunk. This means cur_frame must
+                    # have something in it.
+                    if not cur_frame:
+                        raise Exception("Cannot parse spec, missing parens")
                     if len(cur_frame) == 2:
                         frame = tuple(cur_frame)
                     elif cur_frame[0][0] == '(':
@@ -373,7 +395,12 @@ class Tool:
                 elif c == ')':
                     cur_frame.append(data[start:i + 1].strip())
                     start = i + 1
+                    last_frame_added = start
             i += 1
+
+        # We only permit spaces after the last frame
+        if self.spec[last_frame_added:].strip():
+            raise Exception("Invalid characters found after last frame");
         # improper input
         if count:
             raise Exception("Check your parentheses")
@@ -389,7 +416,9 @@ class Tool:
             func, pred = f[0], f[1]
 
             if not self._validate_predicate(pred):
-                raise Exception
+                raise Exception("Invalid predicate")
+            if not self._validate_identifier(func):
+                raise Exception("Invalid function identifier")
             tup = (pred, absolute_order)
 
             if func not in self.map:
@@ -405,6 +434,16 @@ class Tool:
 
         self.length = absolute_order
 
+    def _validate_identifier(self, func):
+        # We've already established paren balancing. We will only look for
+        # identifier validity here.
+        paren_index = func.find("(")
+        potential_id = func[:paren_index]
+        pattern = '[_a-zA-z][_a-zA-Z0-9]*$'
+        if re.match(pattern, potential_id):
+            return True
+        return False
+
     def _validate_predicate(self, pred):
 
         if len(pred) > 0 and pred[0] == "(":

tools/inject_example.txt

@@ -115,12 +115,12 @@ fail our mounts half the time:
 # ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
 
 USAGE message:
-usage: inject.py [-h] [-I header] [-P probability] [-v] mode spec
+usage: inject.py [-h] [-I header] [-P probability] [-v] {kmalloc,bio} spec
 
 Fail specified kernel functionality when call chain and predicates are met
 
 positional arguments:
-  mode                  indicate which base kernel function to fail
+  {kmalloc,bio}         indicate which base kernel function to fail
   spec                  specify call chain
 
 optional arguments:
@@ -130,3 +130,16 @@ optional arguments:
   -P probability, --probability probability
                         probability that this call chain will fail
   -v, --verbose         print BPF program
+
+EXAMPLES:
+# ./inject.py kmalloc -v 'SyS_mount()'
+    Fails all calls to syscall mount
+# ./inject.py kmalloc -v '(true) => SyS_mount()(true)'
+    Explicit rewriting of above
+# ./inject.py kmalloc -v 'mount_subtree() => btrfs_mount()'
+    Fails btrfs mounts only
+# ./inject.py kmalloc -v 'd_alloc_parallel(struct dentry *parent, const struct \
+    qstr *name)(STRCMP(name->name, 'bananas'))'
+    Fails dentry allocations of files named 'bananas'
+# ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
+    Fails calls to syscall mount with 1% probability