[Poppler-bugs] [Bug 104502] New: I/O errors during checkheader() cause hang

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104502

            Bug ID: 104502
           Summary: I/O errors during checkheader() cause hang
           Product: poppler
           Version: unspecified
          Hardware: All
                OS: Linux (All)
            Status: NEW
          Severity: minor
          Priority: medium
         Component: general
          Assignee: poppler-bugs at lists.freedesktop.org
          Reporter: btimby at gmail.com

Created attachment 136569
  --> https://bugs.freedesktop.org/attachment.cgi?id=136569&action=edit
Check return code of getChar(), abort reading on error.

Hi, I ran into an issue when using pdftotext on files stored on a CIFS mount. A
problem with the CIFS server was causing EIO to be returned for read() calls.
It takes about 1 minute for EIO to be returned, blocking each read() for about
1 minute before it fails.

This caused pdftotext to run for around 16 hours before finally failing. I
tracked this down to PDFDoc::checkHeader(), which attempts to read 1024 chars
using FileStream::getChar() into a buffer. It uses this buffer for file type
detection.

The problem is that it does not check the return code of getChar(). getChar()
returns EOF in response to the EIO, but that EOF is just placed into the
buffer, and another read() is attempted (1024 times) making the process block
in uninterruptible sleep for 16 hours or so.

The fix is to check this return code and stop reading. I am attaching a patch.

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