[PATCH] D58513: [libFuzzer][Windows] Port fork mode to Windows

[Zachary Turner via Phabricator via llvm-commits]

zturner added inline comments.


================
Comment at: compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp:82-83
+  // is very slow on Windows.
+  return (FileAttributes &
+          (FILE_ATTRIBUTE_REPARSE_POINT | FILE_ATTRIBUTE_DIRECTORY)) == 0;
+}
----------------
I mentioned this elsewhere, but reparse point does not imply that the target of the reparse point is a file.  It could be a directory junction, or something else entirely.  Here's all the known reparse tags:

```
#define IO_REPARSE_TAG_MOUNT_POINT              (0xA0000003L)       
#define IO_REPARSE_TAG_HSM                      (0xC0000004L)       
#define IO_REPARSE_TAG_HSM2                     (0x80000006L)       
#define IO_REPARSE_TAG_SIS                      (0x80000007L)       
#define IO_REPARSE_TAG_WIM                      (0x80000008L)       
#define IO_REPARSE_TAG_CSV                      (0x80000009L)       
#define IO_REPARSE_TAG_DFS                      (0x8000000AL)       
#define IO_REPARSE_TAG_SYMLINK                  (0xA000000CL)       
#define IO_REPARSE_TAG_DFSR                     (0x80000012L)       
#define IO_REPARSE_TAG_DEDUP                    (0x80000013L)       
#define IO_REPARSE_TAG_NFS                      (0x80000014L)       
#define IO_REPARSE_TAG_FILE_PLACEHOLDER         (0x80000015L)       
#define IO_REPARSE_TAG_WOF                      (0x80000017L)       
#define IO_REPARSE_TAG_WCI                      (0x80000018L)       
#define IO_REPARSE_TAG_WCI_1                    (0x90001018L)       
#define IO_REPARSE_TAG_GLOBAL_REPARSE           (0xA0000019L)       
#define IO_REPARSE_TAG_CLOUD                    (0x9000001AL)       
#define IO_REPARSE_TAG_CLOUD_1                  (0x9000101AL)       
#define IO_REPARSE_TAG_CLOUD_2                  (0x9000201AL)       
#define IO_REPARSE_TAG_CLOUD_3                  (0x9000301AL)       
#define IO_REPARSE_TAG_CLOUD_4                  (0x9000401AL)       
#define IO_REPARSE_TAG_CLOUD_5                  (0x9000501AL)       
#define IO_REPARSE_TAG_CLOUD_6                  (0x9000601AL)       
#define IO_REPARSE_TAG_CLOUD_7                  (0x9000701AL)       
#define IO_REPARSE_TAG_CLOUD_8                  (0x9000801AL)       
#define IO_REPARSE_TAG_CLOUD_9                  (0x9000901AL)       
#define IO_REPARSE_TAG_CLOUD_A                  (0x9000A01AL)       
#define IO_REPARSE_TAG_CLOUD_B                  (0x9000B01AL)       
#define IO_REPARSE_TAG_CLOUD_C                  (0x9000C01AL)       
#define IO_REPARSE_TAG_CLOUD_D                  (0x9000D01AL)       
#define IO_REPARSE_TAG_CLOUD_E                  (0x9000E01AL)       
#define IO_REPARSE_TAG_CLOUD_F                  (0x9000F01AL)       
#define IO_REPARSE_TAG_CLOUD_MASK               (0x0000F000L)       
#define IO_REPARSE_TAG_APPEXECLINK              (0x8000001BL)       
#define IO_REPARSE_TAG_PROJFS                   (0x9000001CL)       
#define IO_REPARSE_TAG_STORAGE_SYNC             (0x8000001EL)       
#define IO_REPARSE_TAG_WCI_TOMBSTONE            (0xA000001FL)       
#define IO_REPARSE_TAG_UNHANDLED                (0x80000020L)       
#define IO_REPARSE_TAG_ONEDRIVE                 (0x80000021L)       
#define IO_REPARSE_TAG_PROJFS_TOMBSTONE         (0xA0000022L)       
#define IO_REPARSE_TAG_AF_UNIX                  (0x80000023L)       

```


================
Comment at: compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp:212
+        continue;
+      IterateDirRecursive(Path, DirPreCallback, DirPostCallback, FileCallback);
+    } else if (IsFile(PathAttrs) || IsLink(PathAttrs)) {
----------------
Note that this will not follow directory symlinks or junctions.  Is that the desired behavior?


================
Comment at: compiler-rt/lib/fuzzer/FuzzerIOWindows.cpp:213
+      IterateDirRecursive(Path, DirPreCallback, DirPostCallback, FileCallback);
+    } else if (IsFile(PathAttrs) || IsLink(PathAttrs)) {
+      FileCallback(Path);
----------------
This doesn't look correct to me.  You can have a reparse point to something that itself isn't a file.  If it's a link, I think you need to check the reparse tag in `FindInfo.dwReserved0` as described [[ https://docs.microsoft.com/en-us/windows/desktop/api/minwinbase/ns-minwinbase-_win32_find_dataa | here ]]



Repository:
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  https://reviews.llvm.org/D58513/new/

https://reviews.llvm.org/D58513