50782 - ILTRACE core dump in gif.cpp due to LOCAL il_log_module var

Status: VERIFIED FIXED

(Core :: Graphics: ImageLib, defect, P1)

Description

[harbaugh]

(NOTE: proposed fix is included)
'il_log_module' is re-declared locally in gif.cpp and set to NULL.
This causes an attempt to dereference a NULL pointer in the ILTRACE
expansion (files gif.cpp, jpeg.cpp and ipng.cpp).  Hence the program
segfaults before displaying a window.


PROPOSED FIX:
  remove lines 80-81 of gif.cpp, which are actually a *LOCAL*
  redeclaration of variables that should be GLOBAL

    80:   int il_debug;
    81:   PRLogModuleInfo *il_log_module = NULL;

  The 'true' declaration/initialization of these variables occurs
  in ilclient.cpp.  Similar lines should be removed from jpeg.cpp
  and ipng.cpp

  line 80 factors into this because the local 'il_debug' is
  not initialized and hence can contain random junk

========= analysis ===========
Debugger shows that SEGV occurs upon reaching line 859 of gif.cpp:

% ./mozilla -g -d ladebug 
     ./run-mozilla.sh -g -d ladebug ./mozilla-bin 
     MOZILLA_FIVE_HOME=.
      
LD_LIBRARY_PATH=.:/usr/local/fbscapp/inst/gtk128/lib:/usr/local/fbscapp/inst/ORBit051/lib:/usr/local/fbscapp/inst/glib128/lib:/usr/shlib:/usr/ccs/lib:/usr/lib/cmplrs/cc:/
usr/lib:/var/shlib
          LIBRARY_PATH=.
            SHLIB_PATH=.
               LIBPATH=.
            ADDON_PATH=.
           MOZ_PROGRAM=./mozilla-bin
           MOZ_TOOLKIT=
             moz_debug=1
          moz_debugger=ladebug
     /usr/bin/ladebug ./mozilla-bin 
     Welcome to the Ladebug Debugger Version 4.0-62 (built Jun 23 2000)
     ------------------ 
     object file name: ./mozilla-bin 
     core file name: 
     Warning: cannot open core file : 
     Reading symbolic information ...done
     (ladebug) use ../../modules/libimg/gifcom
     Directory search path for source files:
      . ../../modules/libimg/gifcom
     (ladebug) run
     nsNativeComponentLoader: autoregistering begins.
     nsNativeComponentLoader: autoregistering succeeded
     nNCL: registering deferred (0)
     GFX: dpi=96 t2p=0.0666667 p2t=15 depth=16
     WEBSHELL+ = 1
     Initialized app shell component {18c2f989-b09f-11d2-bcde-00805f0e1353},
rv=0x00000000
     Initialized app shell component {33e569b0-40f8-11d4-9a41-000064657374},
rv=0x00000000
     ProfileName : default
     ProfileDir  : /users/primgr/harbaugh/.mozilla/default
     CSSLoaderImpl::LoadAgentSheet: Load of URL
'file:///users/primgr/harbaugh/.mozilla/default/chrome/user.css' failed.  Error
code: 16389
     WEBSHELL+ = 2
     Enabling Quirk StyleSheet
     Note: verifyreflow is disabled
     Note: styleverifytree is disabled
     Note: frameverifytree is disabled
     Enabling Quirk StyleSheet
     WARNING: chrome: failed to get base url for
chrome://necko/locale/necko.properties -- using wacky default, file
nsChromeRegistry.cpp, line 507
     Obtained name of Personal Toolbar from bookmarks string bundle.
     Start reading in bookmarks.html
     Finished reading in bookmarks.html  (78125 microseconds)
     WEBSHELL+ = 3
     Thread received signal SEGV
     stopped at [int il_gif_write(il_container*, const PRUint8*, int32):859
0x3ffbf9140f8]
         859         ILTRACE(9,("il:gif: state %d len %d buf %u p %u q %u ep
%u",


     Preprocessing gif.cpp and examining the output shows *TWO* 
     declarations of il_log_module.  The first is an 'extern'
     from if_struct.h; the second is local (line 81 of gif.cpp)
     and sets il_log_module to NULL.

     Line 859 expands to

        { if(il_debug>1) {do { if (((il_log_module)->level >= (1))) {
PR_LogPrint ("il:gif: ...

     where the attempt to dereference (il_log_module)->level
     SEGFAULTS since the local il_log_module overrides the global.

Comment 1

[harbaugh]

I did test the proposed fix and it works.  The only
question is whether it will adversely affect other platforms.

Comment 2

[jim_nance]

Toni,
    I am attaching the preprocessed output of gif.cpp that you asked me for.
This is with the 6.1 compiler under Tru64 4.0D.

Comment 3

[jim_nance]

Attachment: gif.cpp preprocessor output

Comment 4

[jim_nance]

Attachment: Patch to fix bug

Comment 5

[jim_nance]

pnunn: You look like the person who gets to approve this change if you like it,
and Blame says its your code anyway so thats even better.  I asked for a
reviewer on the newsgroup, so if they say it looks good and you say it looks
good I will check it in.

Comment 6

[Brendan Eich [:brendan]]

This is a slam dunk.  I can review and approve, be good if pnunn gave r= too. 
Please get this in before any branch is cut from the trunk.

/be

Comment 7

[tor]

I would like to see the lines removed as originally proposed instead of
littering libimg with "#if 0" junk.  Clean sweep alternative attached.

Comment 8

[tor]

Attachment: remove extra il_debug and il_log_module definitions

Comment 9

[jim_nance]

Brendan, can you review/approve tor's patch.  He found the same problem in
several other files.

Comment 10

[cls]

We also need to have these global symbol conflicts resolved for static
components (bug 46775) to work.

Comment 11

[pnunn]

r: pnunn
If someone else can check this in. I am swamped.
And some of you Mozillittes can check in easier than
I, a dreaded Netscapian, can.

Comment 12

[Brendan Eich [:brendan]]

a=[e-mail], no brainer.

/be

Comment 13

[jim_nance]

Its already in my tree.  Ill check it (tor's patch) in as soon as the tree opens.

Comment 14

[pnunn]

much thanks.
-p

Comment 15

[jim_nance]

Its checked in

Comment 16

[jim_nance]

This patch breaks the mac.  Should I just #ifdef the code so that its only there
for that platform?

Comment 17

[jim_nance]

Attaching new fix

Comment 18

[jim_nance]

Attachment: A new fix, #ifdefed for mac

Comment 19

[jim_nance]

breandan || pnunn,
   Could one of you review this new patch?

Comment 20

[Scott Collins]

Hmmm.  We're trying to make these local versions of the symbols go away, right?  
If they can't go away on Mac, then we've done something wrong somewhere.  This 
patch may be good enough to get the work in for the other platforms, but to me it 
looks like it means there's still more work to be done on Mac with respect to 
this bug.  I can only r= this patch on the condition that we're still working on 
the right completely cross-platform fix.

Comment 21

[Paul Wyskoczka]

Updating QA Contact

Comment 22

[kinmoz]

Looks like these changes were checked in already ... and they break the Win32 
debug builds. With undefined symbols for il_log_module and il_debug.

You have to also undefine the ILTRACE() macro to get things going again.

Comment 23

[Paul Chen]

As sheriff, I have backed out the changes, caused build bustage on win32, also I
think this can be done xp

Comment 24

[jim_nance]

    The phone company dug through DSL line the other day, so I have been
off the internet for a few days.  I was able to read my email this 
morning only to discover that I broke the debug windows builds on the
27th while trying to fix bug 50872.  I watched tinderbox after I did
that checkin, and they all stayed green so I was quite supprised this
morning to learn that I had broken things.  My guess is that both the
windows tinderbox machines are running optimized builds?  In any event,
after the tinderboxes went green I left, and was not available to help
sort out the bustage I had caused.  I am truly sorry for causing problems.
    This was my second attempt at fixing 50872, and given that I have
broken some platform each time I am now quite scared of trying again.
I am only able to test my code under Linux, and that is obviously not
sufficient for this code.  I am going to see if I can find someone at
NS who has access to all 3 platforms to take ownership of this bug.

Comment 25

[Shanjian Li]

Why not just remove those il_debug, il_log_module and ILTRACE from gif.cpp, 
ipng.cpp, jpeg.cpp. We just lost some debug information. That should solve
all the problem. If somebody believe it is really necessary to have those
information, we may have to define local version in different names, like
ipng_log_module, ipng_debug, IPNG_TRACE. For those small modules, I doubt
its necessity.

Comment 26

[jim_nance]

*** Bug 62024 has been marked as a duplicate of this bug. ***

Comment 27

[Keyser Sose]

*** Bug 67865 has been marked as a duplicate of this bug. ***

Comment 28

[Keyser Sose]

Whats the progress on this bug were still seeing people having this crash on them.

Comment 29

[jim_nance]

There has been no progress as far as I know.  We know whats going on, and
several proposals to fix this have been put on the table.  Someone with some
athority (pnunn?) needs to pick one. FWIW, I like Shanjian Li's proposal the
best.  Lets just remove this code.  We dont need it and its causing problems.

Comment 30

[cls]

Attachment: Create uniquely named debug variables for each img component

Comment 31

[cls]

Taking bug.

Comment 32

[Steve Dagley]

Verified 03/18/01 ptach on Mac debug for gif, jpg, mng and png decoder projects 
as wells as libimg project.  Still need verification on opt build

Comment 33

[cls]

Verified debug & opt on win32.

Comment 34

[tor]

sr=tor

Comment 35

[Stuart Parmenter]

r=pavlov

Comment 36

[cls]

Patch checked in.  Marking fixed.

Comment 37

[Terri Preston]

Verified fix checked into lxr.mozilla.org