[PATCH 5.4 019/102] powerpc/security: Fix debugfs data leak on 32-bit

Greg Kroah-Hartman
2020-01-24T09:38:27Z

From: Geert Uytterhoeven <geert+renesas@glider.be>

commit 3b05a1e517e1a8cfda4866ec31d28b2bc4fee4c4 upstream.

"powerpc_security_features" is "unsigned long", i.e. 32-bit or 64-bit,
depending on the platform (PPC_FSL_BOOK3E or PPC_BOOK3S_64). Hence
casting its address to "u64 *", and calling debugfs_create_x64() is
wrong, and leaks 32-bit of nearby data to userspace on 32-bit platforms.

While all currently defined SEC_FTR_* security feature flags fit in
32-bit, they all have "ULL" suffixes to make them 64-bit constants.
Hence fix the leak by changing the type of "powerpc_security_features"
(and the parameter types of its accessors) to "u64". This also allows
to drop the cast.

Fixes: 398af571128fe75f ("powerpc/security: Show powerpc_security_features in debugfs")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191021142309.28105-1-geert+renesas@glider.be
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/powerpc/include/asm/security_features.h | 8 ++++----
arch/powerpc/kernel/security.c | 4 ++--
2 files changed, 6 insertions(+), 6 deletions(-)

--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -9,7 +9,7 @@
#define _ASM_POWERPC_SECURITY_FEATURES_H

-extern unsigned long powerpc_security_features;
+extern u64 powerpc_security_features;
extern bool rfi_flush;

/* These are bit flags */
@@ -24,17 +24,17 @@ void setup_stf_barrier(void);
void do_stf_barrier_fixups(enum stf_barrier_type types);
void setup_count_cache_flush(void);

-static inline void security_ftr_set(unsigned long feature)
+static inline void security_ftr_set(u64 feature)
{
powerpc_security_features |= feature;
}

-static inline void security_ftr_clear(unsigned long feature)
+static inline void security_ftr_clear(u64 feature)
{
powerpc_security_features &= ~feature;
}

-static inline bool security_ftr_enabled(unsigned long feature)
+static inline bool security_ftr_enabled(u64 feature)
{
return !!(powerpc_security_features & feature);
}
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -16,7 +16,7 @@
#include <asm/setup.h>

-unsigned long powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;
+u64 powerpc_security_features __read_mostly = SEC_FTR_DEFAULT;

enum count_cache_flush_type {
COUNT_CACHE_FLUSH_NONE = 0x1,
@@ -109,7 +109,7 @@ device_initcall(barrier_nospec_debugfs_i
static __init int security_feature_debugfs_init(void)
{
debugfs_create_x64("security_features", 0400, powerpc_debugfs_root,
- (u64 *)&powerpc_security_features);
+ &powerpc_security_features);
return 0;
}
device_initcall(security_feature_debugfs_init);