MIPS: Don't clobber personality high bits.

The high bits of current->personality carry settings that we don't want to
clobber on each exec.  Only clobber them if the lower bits that indicate
either PER_LINUX or PER_LINUX32 are invalid.

The clobbering prevents us from using useful bits like ADDR_NO_RANDOMIZE.

Reported-by: Camm Maguire <camm@maguirefamily.org>
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: Camm Maguire <camm@maguirefamily.org>
Patchwork: https://patchwork.linux-mips.org/patch/1750/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index fd1d39eb7431..455c0ac7d4ea 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -249,7 +249,8 @@ extern struct mips_abi mips_abi_n32;
 
 #define SET_PERSONALITY(ex)                                             \
 do {                                                                    \
-        set_personality(PER_LINUX);                                     \
+        if (personality(current->personality) != PER_LINUX)             \
+                set_personality(PER_LINUX);                             \
                                                                         \
         current->thread.abi = &mips_abi;                                \
 } while (0)
@@ -296,6 +297,8 @@ do {									\
 
 #define SET_PERSONALITY(ex)                                             \
 do {                                                                    \
+        unsigned int p;                                                 \
+                                                                        \
         clear_thread_flag(TIF_32BIT_REGS);                              \
         clear_thread_flag(TIF_32BIT_ADDR);                              \
                                                                         \
@@ -304,7 +307,8 @@ do {									\
         else                                                            \
                 current->thread.abi = &mips_abi;                        \
                                                                         \
-        if (current->personality != PER_LINUX32)                        \
+        p = personality(current->personality);                          \
+        if (p != PER_LINUX32 && p != PER_LINUX)                         \
                 set_personality(PER_LINUX);                             \
 } while (0)