[Bug 1001635] New: wrong results from Cyg_StdioStream::read

[Bug 1001635] New: wrong results from Cyg_StdioStream::read

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           Summary: wrong results from Cyg_StdioStream::read
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: normal
         Component: C library
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: bernd.edlinger@hotmail.de
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


Created an attachment (id=1849)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1849)
proposed patch to fix this defect.

there are several different code paths which can lead to wrong results
in the function Cyg_StdioStream::read().

Please have a look at the following file:
"ecos/packages/language/c/libc/stdio/current/src/common/stream.cxx".

Suppose we are in unbuffered mode.
There may be an unread character in the "ungetc" buffer.
And there may be an unread character in the "readbuf_char" buffer.

Then the code may go thru the if statement in line 340, and
later thru the if statement in line 382.
BUG: in line 384: *bytes_read = 1; is wrong, we have 2 bytes read.

Now suppose we are in unbuffered mode again.
There may be an unread character in the "ungetc" buffer.
And the buffer_length may be 3 or higher.

Then the code may go thru the if statement in line 340, and
later thru the if statement in line 394.
BUG: user_buffer was already incremented in line 341. So the returned
data will contain an uninitialized byte in the middle.

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[Bug 1001635] New: wrong results from Cyg_StdioStream::read

[bugzilla-daemon]

Please do not reply to this email. Use the web interface provided at:
http://bugs.ecos.sourceware.org/show_bug.cgi?id=1001635

           Summary: wrong results from Cyg_StdioStream::read
           Product: eCos
           Version: CVS
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: normal
         Component: C library
        AssignedTo: unassigned@bugs.ecos.sourceware.org
        ReportedBy: bernd.edlinger@hotmail.de
                CC: ecos-bugs@ecos.sourceware.org
             Class: Advice Request


Created an attachment (id=1849)
 --> (http://bugs.ecos.sourceware.org/attachment.cgi?id=1849)
proposed patch to fix this defect.

there are several different code paths which can lead to wrong results
in the function Cyg_StdioStream::read().

Please have a look at the following file:
"ecos/packages/language/c/libc/stdio/current/src/common/stream.cxx".

Suppose we are in unbuffered mode.
There may be an unread character in the "ungetc" buffer.
And there may be an unread character in the "readbuf_char" buffer.

Then the code may go thru the if statement in line 340, and
later thru the if statement in line 382.
BUG: in line 384: *bytes_read = 1; is wrong, we have 2 bytes read.

Now suppose we are in unbuffered mode again.
There may be an unread character in the "ungetc" buffer.
And the buffer_length may be 3 or higher.

Then the code may go thru the if statement in line 340, and
later thru the if statement in line 394.
BUG: user_buffer was already incremented in line 341. So the returned
data will contain an uninitialized byte in the middle.

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