Please backport commit e74deb11931ff682b59d5b9d387f7115f689698e to
stable _or_ revert the backport of commit 4a6c91fbdef84 ("x86/uaccess,
ftrace: Fix ftrace_likely_update() vs. SMAP"). It uses
user_access_{save|restore}() which has been introduced in the following
commit.
I stumbled upon it in latest v5.0 tree and verified that v5.1.15 is also
affected. For reference, the commit I'm asking to backport.
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
[ Upstream change e74deb11931ff682b59d5b9d387f7115f689698e ]
Introduce common helpers for when we need to safely suspend a
uaccess section; for instance to generate a {KA,UB}SAN report.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
arch/x86/include/asm/smap.h | 20 ++++++++++++++++++++
arch/x86/include/asm/uaccess.h | 3 +++
include/linux/uaccess.h | 2 ++
3 files changed, 25 insertions(+)
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
index db333300bd4be..6cfe431710203 100644
--- a/arch/x86/include/asm/smap.h
+++ b/arch/x86/include/asm/smap.h
@@ -58,6 +58,23 @@ static __always_inline void stac(void)
alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP);
}
+static __always_inline unsigned long smap_save(void)
+{
+ unsigned long flags;
+
+ asm volatile (ALTERNATIVE("", "pushf; pop %0; " __stringify(__ASM_CLAC),
+ X86_FEATURE_SMAP)
+ : "=rm" (flags) : : "memory", "cc");
+
+ return flags;
+}
+
+static __always_inline void smap_restore(unsigned long flags)
+{
+ asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP)
+ : : "g" (flags) : "memory", "cc");
+}
+
/* These macros can be used in asm() statements */
#define ASM_CLAC \
ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP)
@@ -69,6 +86,9 @@ static __always_inline void stac(void)
static inline void clac(void) { }
static inline void stac(void) { }
+static inline unsigned long smap_save(void) { return 0; }
+static inline void smap_restore(unsigned long flags) { }
+
#define ASM_CLAC
#define ASM_STAC
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 3822cc8ac9d6d..e34cd97cb9a01 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -716,6 +716,9 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t
#define user_access_begin(a,b) user_access_begin(a,b)
#define user_access_end() __uaccess_end()
+#define user_access_save() smap_save()
+#define user_access_restore(x) smap_restore(x)
+
#define unsafe_put_user(x, ptr, label) \
__put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label)
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 37b226e8df13f..2b70130af5857 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -268,6 +268,8 @@ extern long strncpy_from_unsafe(char *dst, const void *unsafe_addr, long count);
#define user_access_end() do { } while (0)
#define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0)
#define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0)
+static inline unsigned long user_access_save(void) { return 0UL; }
+static inline void user_access_restore(unsigned long flags) { }
#endif
#ifdef CONFIG_HARDENED_USERCOPY
--
2.20.1
