#592 gendef segfaults when running on OpenWatcom-built dlls

[Ozkan Sezer]

gendef segfaults when running on OpenWatcom-built dlls.

With something simple as this:

$ cat 1.c
void __declspec(dllexport) foo(void) {}
$ wcc386 -bt=nt -bd -3s -q 1.c
$ wlink NAM 1.dll SYSTEM nt_dll FIL {1.o}
[...]
$ gdb --args ./gendef 1.dll
[...]
Starting program: /home/sezero/gendef/gendef 1.dll

 * [1.dll] Found PE image
 * export directory at VA = 0xb000 size=0x3e

Program received signal SIGSEGV, Segmentation fault.
0x080499ad in do_export_read (va_exp=45056, sz_exp=62, be64=0) at src/gendef.c:570
570   fndllname = strdup ((char *) map_va (exp_dir->Name));
(gdb) bt
#0  0x080499ad in do_export_read (va_exp=45056, sz_exp=62, be64=0) at src/gendef.c:570
#1  0x08049709 in do_pedef () at src/gendef.c:478
#2  0x08048df6 in main (argc=2, argv=0xbfb0e3d4) at src/gendef.c:231

The example 1.dll is attached.

[Ozkan Sezer]

Obviously map_va() returns NULL for exp_dir and exp_dir->Name
becomes a NULL pointer dereference. Now, why do we get NULL from
map_va()..

Kai?

P.S.: Curiously, the pexports tool from mingw.org woks fine with these dlls.

[Kai Tietz]

No idea. Sadly I don't have time to look into this. Debugging map_va doesn't reveal here anything?

[Ozkan Sezer]

Kai:

Some sections seem to have Misc.VirtualSize==0, therefore map_va()
skips them and when there are none left it returns NULL.

I made a patch (inlined below, also attached) so if Misc.VirtualSize
is zero it would use SizeOfRawData instead. With this, gendef does
not crash and generates the def.

diff --git a/mingw-w64-tools/gendef/src/gendef.c b/mingw-w64-tools/gendef/src/gendef.c
index d70c1ad..cc5e120 100644
--- a/mingw-w64-tools/gendef/src/gendef.c
+++ b/mingw-w64-tools/gendef/src/gendef.c
@@ -432,7 +432,7 @@ static void *
 map_va (uint32_t va)
 {
   PIMAGE_SECTION_HEADER sec;

-  uint32_t sec_cnt,i;
+  uint32_t sec_cnt,sz,i;
   char *dptr;

   if (gPEDta)
@@ -447,7 +447,9 @@ map_va (uint32_t va)
     }
   for (i = 0;i < sec_cnt;i++)
     {

-      if (va >= sec[i].VirtualAddress && va < (sec[i].VirtualAddress+sec[i].Misc.VirtualSize))
+      sz = sec[i].Misc.VirtualSize;
+      if (!sz) sz = sec[i].SizeOfRawData;
+      if (va >= sec[i].VirtualAddress && va < (sec[i].VirtualAddress+sz))
         {
           dptr = (char *) &gDta[va-sec[i].VirtualAddress+sec[i].PointerToRawData];
           return (void *)dptr; 

Comments? Is the patch correct?

[Kai Tietz]

Patch looks sensible to me. Please go ahead and apply it to master.
I guess this fix will be something for open branches, too.

Thanks,
Kai

2017-03-07 13:29 GMT+01:00 Ozkan Sezer sezero@users.sf.net:

Kai:

Some sections seem to have Misc.VirtualSize==0, therefore map_va()
skips them and when there are none left it returns NULL.

I made a patch (inlined below, also attached) so if Misc.VirtualSize
is zero it would use SizeOfRawData instead. With this, gendef does
not crash and generates the def.

diff --git a/mingw-w64-tools/gendef/src/gendef.c
b/mingw-w64-tools/gendef/src/gendef.c
index d70c1ad..cc5e120 100644
--- a/mingw-w64-tools/gendef/src/gendef.c
+++ b/mingw-w64-tools/gendef/src/gendef.c
@@ -432,7 +432,7 @@ static void *
map_va (uint32_t va)
{
PIMAGE_SECTION_HEADER sec;
- uint32_t sec_cnt,i;
+ uint32_t sec_cnt,sz,i;
char *dptr;

if (gPEDta)
@@ -447,7 +447,9 @@ map_va (uint32_t va)
}
for (i = 0;i < sec_cnt;i++)
{
- if (va >= sec[i].VirtualAddress && va <
(sec[i].VirtualAddress+sec[i].Misc.VirtualSize))
+ sz = sec[i].Misc.VirtualSize;
+ if (!sz) sz = sec[i].SizeOfRawData;
+ if (va >= sec[i].VirtualAddress && va < (sec[i].VirtualAddress+sz))
{
dptr = (char )
&gDta[va-sec[i].VirtualAddress+sec[i].PointerToRawData];
return (void )dptr;

Comments? Is the patch correct?

Attachments:

gendef-test.patch (835 Bytes; application/octet-stream)

---

[bugs:#592] gendef segfaults when running on OpenWatcom-built dlls

Status: open
Group: v1.0 (example)
Created: Sun Mar 05, 2017 08:29 PM UTC by Ozkan Sezer
Last Updated: Mon Mar 06, 2017 02:48 PM UTC
Owner: nobody
Attachments:

1.dll.7z (13.8 kB; application/octet-stream)

gendef segfaults when running on OpenWatcom-built dlls.

With something simple as this:

$ cat 1.c
void __declspec(dllexport) foo(void) {}
$ wcc386 -bt=nt -bd -3s -q 1.c
$ wlink NAM 1.dll SYSTEM nt_dll FIL {1.o}
[...]
$ gdb --args ./gendef 1.dll
[...]
Starting program: /home/sezero/gendef/gendef 1.dll
* [1.dll] Found PE image
* export directory at VA = 0xb000 size=0x3e

Program received signal SIGSEGV, Segmentation fault.
0x080499ad in do_export_read (va_exp=45056, sz_exp=62, be64=0) at
src/gendef.c:570
570 fndllname = strdup ((char *) map_va (exp_dir->Name));
(gdb) bt

0 0x080499ad in do_export_read (va_exp=45056, sz_exp=62, be64=0) at

src/gendef.c:570

1 0x08049709 in do_pedef () at src/gendef.c:478

2 0x08048df6 in main (argc=2, argv=0xbfb0e3d4) at src/gendef.c:231

The example 1.dll is attached.

---

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[Ozkan Sezer]

Patch applied to master and all branches. Closing as fixed.