In preparation of implementing user_access_begin and friends
on powerpc, the book3s/32 version of prevent_user_access() need
to be prepared for user_access_end().
user_access_end() doesn't provide the address and size which
were passed to user_access_begin(), required by prevent_user_access()
to know which segment to modify.
The list of segments which where unprotected by allow_user_access()
are available in current->kuap. But we don't want prevent_user_access()
to read this all the time, especially everytime it is 0 (for instance
because the access was not a write access).
Implement a special direction named KUAP_CURRENT. In this case only,
the addr and end are retrieved from current->kuap.
Signed-off-by: Christophe Leroy <[email protected]>
---
v2: No change
v3: This patch was not in v3
v4: Added build protection against bad use of KUAP_CURRENT.
---
arch/powerpc/include/asm/book3s/32/kup.h | 23 +++++++++++++++----
.../powerpc/include/asm/book3s/64/kup-radix.h | 4 +++-
arch/powerpc/include/asm/kup.h | 11 +++++++++
3 files changed, 32 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index de29fb752cca..17e069291c72 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -108,6 +108,8 @@ static __always_inline void allow_user_access(void __user *to, const void __user
u32 addr, end;
BUILD_BUG_ON(!__builtin_constant_p(dir));
+ BUILD_BUG_ON(dir == KUAP_CURRENT);
+
if (!(dir & KUAP_WRITE))
return;
@@ -117,6 +119,7 @@ static __always_inline void allow_user_access(void __user *to, const void __user
return;
end = min(addr + size, TASK_SIZE);
+
current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
}
@@ -127,15 +130,25 @@ static __always_inline void prevent_user_access(void __user *to, const void __us
u32 addr, end;
BUILD_BUG_ON(!__builtin_constant_p(dir));
- if (!(dir & KUAP_WRITE))
- return;
- addr = (__force u32)to;
+ if (dir == KUAP_CURRENT) {
+ u32 kuap = current->thread.kuap;
- if (unlikely(addr >= TASK_SIZE || !size))
+ if (unlikely(!kuap))
+ return;
+
+ addr = kuap & 0xf0000000;
+ end = kuap << 28;
+ } else if (dir & KUAP_WRITE) {
+ addr = (__force u32)to;
+ end = min(addr + size, TASK_SIZE);
+
+ if (unlikely(addr >= TASK_SIZE || !size))
+ return;
+ } else {
return;
+ }
- end = min(addr + size, TASK_SIZE);
current->thread.kuap = 0;
kuap_update_sr(mfsrin(addr) | SR_KS, addr, end); /* set Ks */
}
diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
index c8d1076e0ebb..a0263e94df33 100644
--- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
@@ -86,8 +86,10 @@ static __always_inline void allow_user_access(void __user *to, const void __user
set_kuap(AMR_KUAP_BLOCK_WRITE);
else if (dir == KUAP_WRITE)
set_kuap(AMR_KUAP_BLOCK_READ);
- else
+ else if (dir == KUAP_READ_WRITE)
set_kuap(0);
+ else
+ BUILD_BUG();
}
static inline void prevent_user_access(void __user *to, const void __user *from,
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 94f24928916a..c3ce7e8ae9ea 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -5,6 +5,12 @@
#define KUAP_READ 1
#define KUAP_WRITE 2
#define KUAP_READ_WRITE (KUAP_READ | KUAP_WRITE)
+/*
+ * For prevent_user_access() only.
+ * Use the current saved situation instead of the to/from/size params.
+ * Used on book3s/32
+ */
+#define KUAP_CURRENT 4
#ifdef CONFIG_PPC64
#include <asm/book3s/64/kup-radix.h>
@@ -88,6 +94,11 @@ static inline void prevent_read_write_user(void __user *to, const void __user *f
prevent_user_access(to, from, size, KUAP_READ_WRITE);
}
+static inline void prevent_current_access_user(void)
+{
+ prevent_user_access(NULL, NULL, ~0UL, KUAP_CURRENT);
+}
+
#endif /* !__ASSEMBLY__ */
#endif /* _ASM_POWERPC_KUAP_H_ */
--
2.25.0