[RFA/HPUX] somread.c: avoid stack overflow

[RFA/HPUX] somread.c: avoid stack overflow

[Joel Brobecker]

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Hello,

A customer of ours ran into a GDB crash that was caused by a stack
overflow. Their executables are very large, and it turned out when
we started debugging that the overflow happened during an alloca
besides which there already was a FIXME:.

We replace the calls to alloca by a call to xmalloc followed by
make_cleanup and the problem was gone.

2006-10-04  Joel Brobecker  <brobecker@adacore.com>

        * somread.c (som_symtab_read): Avoid using alloca for potentially
        large buffers.

Tested on pa-hpux, no regression.

OK to commit?

Thanks,
-- 
Joel

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Index: somread.c
===================================================================
RCS file: /cvs/src/src/gdb/somread.c,v
retrieving revision 1.30
diff -u -p -r1.30 somread.c
--- somread.c	1 Mar 2006 05:47:46 -0000	1.30
+++ somread.c	4 Oct 2006 18:20:41 -0000
@@ -88,15 +88,22 @@ som_symtab_read (bfd *abfd, struct objfi
 
   number_of_symbols = bfd_get_symcount (abfd);
 
-  /* FIXME (alloca): could be quite large. */
-  buf = alloca (symsize * number_of_symbols);
+  /* Allocate a buffer to read in the debug info.
+     We avoid using alloca because the memory size could be so large
+     that we could hit the stack size limit.  */
+  buf = xmalloc (symsize * number_of_symbols);
+  make_cleanup (xfree, buf);
   bfd_seek (abfd, obj_som_sym_filepos (abfd), SEEK_SET);
   val = bfd_bread (buf, symsize * number_of_symbols, abfd);
   if (val != symsize * number_of_symbols)
     error (_("Couldn't read symbol dictionary!"));
 
-  /* FIXME (alloca): could be quite large. */
-  stringtab = alloca (obj_som_stringtab_size (abfd));
+  /* Allocate a buffer to read in the som stringtab section of
+     the debugging info.  Again, we avoid using alloca because
+     the data could be so large that we could potentially hit
+     the stack size limitat.  */
+  stringtab = xmalloc (obj_som_stringtab_size (abfd));
+  make_cleanup (xfree, stringtab);
   bfd_seek (abfd, obj_som_str_filepos (abfd), SEEK_SET);
   val = bfd_bread (stringtab, obj_som_stringtab_size (abfd), abfd);
   if (val != obj_som_stringtab_size (abfd))

Re: [RFA/HPUX] somread.c: avoid stack overflow

[Mark Kettenis]

> Date: Wed, 4 Oct 2006 11:25:05 -0700
> From: Joel Brobecker <brobecker@adacore.com>
> 
> Hello,
> 
> A customer of ours ran into a GDB crash that was caused by a stack
> overflow. Their executables are very large, and it turned out when
> we started debugging that the overflow happened during an alloca
> besides which there already was a FIXME:.
> 
> We replace the calls to alloca by a call to xmalloc followed by
> make_cleanup and the problem was gone.
> 
> 2006-10-04  Joel Brobecker  <brobecker@adacore.com>
> 
>         * somread.c (som_symtab_read): Avoid using alloca for potentially
>         large buffers.
> 
> Tested on pa-hpux, no regression.
> 
> OK to commit?

Looks reasonable to me.

Re: [RFA/HPUX] somread.c: avoid stack overflow

[Joel Brobecker]

> > 2006-10-04  Joel Brobecker  <brobecker@adacore.com>
> > 
> >         * somread.c (som_symtab_read): Avoid using alloca for potentially
> >         large buffers.
> > 
> 
> Looks reasonable to me.

Thanks Mark. This one is now checked in.

-- 
Joel