linux-kernel - [RFC PATCH] Keep 3 high personality bytes across exec

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Message-ID: <20080618060651.GA8251@us.ibm.com>
Date:	Tue, 17 Jun 2008 23:06:51 -0700
From:	Eric B Munson <ebmunson@...ibm.com>
To:	linuxppc-dev@...abs.org
Cc:	linux-kernel@...r.kernel.org
Subject: [RFC PATCH] Keep 3 high personality bytes across exec

Currently when a 32 bit process is exec'd on a powerpc 64 bit host the values
of the top three bytes of the personality are clobbered.  This patch adds a
check in the SET_PERSONALITY macro that will carry all the values in the top
three bytes across the exec.

Signed-off-by: Eric B Munson <ebmunson@...ibm.com>

---

Based on 2.6.26-rc6

 include/asm-powerpc/elf.h   |    3 ++-
 include/linux/personality.h |    6 ++++++
 2 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/include/asm-powerpc/elf.h b/include/asm-powerpc/elf.h
index 9080d85..2f11a0e 100644
--- a/include/asm-powerpc/elf.h
+++ b/include/asm-powerpc/elf.h
@@ -257,7 +257,8 @@ do {								\
 	else							\
 		clear_thread_flag(TIF_ABI_PENDING);		\
 	if (personality(current->personality) != PER_LINUX32)	\
-		set_personality(PER_LINUX);			\
+		set_personality(PER_LINUX |			\
+			(current->personality & PER_INHERIT));	\
 } while (0)
 /*
  * An executable for which elf_read_implies_exec() returns TRUE will
diff --git a/include/linux/personality.h b/include/linux/personality.h
index a84e9ff..362eb90 100644
--- a/include/linux/personality.h
+++ b/include/linux/personality.h
@@ -36,6 +36,12 @@ enum {
 	ADDR_LIMIT_3GB = 	0x8000000,
 };
 
+/* Mask for the above personality values */
+#define PER_INHERIT (ADDR_NO_RANDOMIZE|FDPIC_FUNCPTRS|MMAP_PAGE_ZERO| \
+			ADDR_COMPAT_LAYOUT|READ_IMPLIES_EXEC|ADDR_LIMIT_32BIT| \
+			SHORT_INODE|WHOLE_SECONDS|STICKY_TIMEOUTS| \
+			ADDR_LIMIT_3GB)
+
 /*
  * Security-relevant compatibility flags that must be
  * cleared upon setuid or setgid exec:


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