[reactos] 05/05: [NTOSKRNL] Properly copy backtracking buffer content on realloc

[Bartosz Brachaczek]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=8bc9935fcb334bb7c393f3...

commit 8bc9935fcb334bb7c393f33cd8e3b708a6d31518
Author:     Bartosz Brachaczek [e-mail]
AuthorDate: Sun Mar 31 11:42:56 2019 +0200
Commit:     Pierre Schweitzer [e-mail]
CommitDate: Sun Mar 31 11:44:01 2019 +0200

[NTOSKRNL] Properly copy backtracking buffer content on realloc

CORE-15902
---
 ntoskrnl/fsrtl/dbcsname.c | 22 +++++++++++-----------
 ntoskrnl/fsrtl/name.c     | 22 +++++++++++-----------
 2 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/ntoskrnl/fsrtl/dbcsname.c b/ntoskrnl/fsrtl/dbcsname.c
index d44fde9cc0..2c7300f388 100644
--- a/ntoskrnl/fsrtl/dbcsname.c
+++ b/ntoskrnl/fsrtl/dbcsname.c
@@ -305,21 +305,21 @@ FsRtlIsDbcsInExpression(IN PANSI_STRING Expression,
                         goto Exit;
                     }

-                    /* Backtracking is at the start of the buffer */
-                    BackTracking = AllocatedBuffer;
-
-                    /* Copy BackTrackingBuffer content */
-                    RtlCopyMemory(BackTracking,
-                                  BackTrackingBuffer,
+                    /* Copy BackTracking content. Note that it can point to either BackTrackingBuffer or OldBackTrackingBuffer */
+                    RtlCopyMemory(AllocatedBuffer,
+                                  BackTracking,
                                   RTL_NUMBER_OF(BackTrackingBuffer) * sizeof(USHORT));

-                    /* OldBackTracking is after BackTracking */
-                    OldBackTracking = &BackTracking[BackTrackingBufferSize];
+                    /* Place current Backtracking is at the start of the new buffer */
+                    BackTracking = AllocatedBuffer;

-                    /* Copy OldBackTrackingBuffer content */
-                    RtlCopyMemory(OldBackTracking,
-                                  OldBackTrackingBuffer,
+                    /* Copy OldBackTracking content */
+                    RtlCopyMemory(&BackTracking[BackTrackingBufferSize],
+                                  OldBackTracking,
                                   RTL_NUMBER_OF(OldBackTrackingBuffer) * sizeof(USHORT));
+
+                    /* Place current OldBackTracking after current BackTracking in the buffer */
+                    OldBackTracking = &BackTracking[BackTrackingBufferSize];
                 }

/* If lead byte present */
diff --git a/ntoskrnl/fsrtl/name.c b/ntoskrnl/fsrtl/name.c
index ae934900f4..6a2c280cd1 100644
--- a/ntoskrnl/fsrtl/name.c
+++ b/ntoskrnl/fsrtl/name.c
@@ -157,21 +157,21 @@ FsRtlIsNameInExpressionPrivate(IN PUNICODE_STRING Expression,
                         goto Exit;
                     }

-                    /* Backtracking is at the start of the buffer */
-                    BackTracking = AllocatedBuffer;
-
-                    /* Copy BackTrackingBuffer content */
-                    RtlCopyMemory(BackTracking,
-                                  BackTrackingBuffer,
+                    /* Copy BackTracking content. Note that it can point to either BackTrackingBuffer or OldBackTrackingBuffer */
+                    RtlCopyMemory(AllocatedBuffer,
+                                  BackTracking,
                                   RTL_NUMBER_OF(BackTrackingBuffer) * sizeof(USHORT));

-                    /* OldBackTracking is after BackTracking */
-                    OldBackTracking = &BackTracking[BackTrackingBufferSize];
+                    /* Place current Backtracking is at the start of the new buffer */
+                    BackTracking = AllocatedBuffer;

-                    /* Copy OldBackTrackingBuffer content */
-                    RtlCopyMemory(OldBackTracking,
-                                  OldBackTrackingBuffer,
+                    /* Copy OldBackTracking content */
+                    RtlCopyMemory(&BackTracking[BackTrackingBufferSize],
+                                  OldBackTracking,
                                   RTL_NUMBER_OF(OldBackTrackingBuffer) * sizeof(USHORT));
+
+                    /* Place current OldBackTracking after current BackTracking in the buffer */
+                    OldBackTracking = &BackTracking[BackTrackingBufferSize];
                 }

/* Basic check to test if chars are equal */