[ros-diffs] [reactos] 02/02: [NTOSKRNL] Do not try to access OldBackTracking[-1]

[Bartosz Brachaczek]

https://git.reactos.org/?p=reactos.git;a=commitdiff;h=d256ff60068cafca0d3dc…

commit d256ff60068cafca0d3dc78f518b6617b786efe0
Author:     Bartosz Brachaczek <b.brachaczek(a)gmail.com>
AuthorDate: Mon Apr 1 02:09:23 2019 +0200
Commit:     Pierre Schweitzer <pierre(a)reactos.org>
CommitDate: Mon Apr 1 08:28:00 2019 +0200

    [NTOSKRNL] Do not try to access OldBackTracking[-1]
    
    It can be triggered by the existing "F<", "FILE.TXT" case in
the tests.
    
    CORE-15902
---
 ntoskrnl/fsrtl/dbcsname.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ntoskrnl/fsrtl/dbcsname.c b/ntoskrnl/fsrtl/dbcsname.c
index 3b1afd801e..362549e30b 100644
--- a/ntoskrnl/fsrtl/dbcsname.c
+++ b/ntoskrnl/fsrtl/dbcsname.c
@@ -248,7 +248,7 @@ FsRtlIsDbcsInExpression(IN PANSI_STRING Expression,
         if (NamePosition >= Name->Length)
         {
             EndOfName = TRUE;
-            if (OldBackTracking[MatchingChars - 1] == Expression->Length * 2)
+            if (MatchingChars && OldBackTracking[MatchingChars - 1] ==
Expression->Length * 2)
                 break;
         }
         else
@@ -422,7 +422,7 @@ FsRtlIsDbcsInExpression(IN PANSI_STRING Expression,
     }
 
     /* Store result value */
-    Result = (OldBackTracking[MatchingChars - 1] == Expression->Length * 2);
+    Result = MatchingChars && (OldBackTracking[MatchingChars - 1] ==
Expression->Length * 2);
 
 Exit: