[PPC64] Fix for 32-bit execve() error path

[David Gibson]

Andrew, please apply.

The patch below fixes a bug in ppc64's 32-bit execve() path.  It
duplicates logic already in the normal fs/exec.c do_execve() to avoid
dropping a NULL mm.  The bprm.mm becomes NULL once the exec passes the
"point of no return".  Without this patch a failure past that point
(e.g. mmap() failure) will cause an oops, with it just a killed
process.

diff -urN ppc64-linux-2.5/arch/ppc64/kernel/sys_ppc32.c linux-gogogo/arch/ppc64/kernel/sys_ppc32.c
--- ppc64-linux-2.5/arch/ppc64/kernel/sys_ppc32.c	2004-01-19 14:20:32.484450172 +1100
+++ linux-gogogo/arch/ppc64/kernel/sys_ppc32.c	2004-01-20 14:15:02.093551035 +1100
@@ -2084,7 +2084,8 @@
 		security_bprm_free(&bprm);

 out_mm:
-	mmdrop(bprm.mm);
+	if (bprm.mm)
+		mmdrop(bprm.mm);

 out_file:
 	if (bprm.file) {

--
David Gibson			| For every complex problem there is a
david AT gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.
http://www.ozlabs.org/people/dgibson

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