[PATCH v4 3/7] powerpc/kuap: Fix set direction in allow/prevent_user_access()
From: Christophe Leroy
Date: Fri Jan 24 2020 - 06:54:48 EST
__builtin_constant_p() always return 0 for pointers, so on RADIX
we always end up opening both direction (by writing 0 in SPR29):
0000000000000170 <._copy_to_user>:
...
1b0: 4c 00 01 2c isync
1b4: 39 20 00 00 li r9,0
1b8: 7d 3d 03 a6 mtspr 29,r9
1bc: 4c 00 01 2c isync
1c0: 48 00 00 01 bl 1c0 <._copy_to_user+0x50>
1c0: R_PPC64_REL24 .__copy_tofrom_user
...
0000000000000220 <._copy_from_user>:
...
2ac: 4c 00 01 2c isync
2b0: 39 20 00 00 li r9,0
2b4: 7d 3d 03 a6 mtspr 29,r9
2b8: 4c 00 01 2c isync
2bc: 7f c5 f3 78 mr r5,r30
2c0: 7f 83 e3 78 mr r3,r28
2c4: 48 00 00 01 bl 2c4 <._copy_from_user+0xa4>
2c4: R_PPC64_REL24 .__copy_tofrom_user
...
Use an explicit parameter for direction selection, so that GCC
is able to see it is a constant:
00000000000001b0 <._copy_to_user>:
...
1f0: 4c 00 01 2c isync
1f4: 3d 20 40 00 lis r9,16384
1f8: 79 29 07 c6 rldicr r9,r9,32,31
1fc: 7d 3d 03 a6 mtspr 29,r9
200: 4c 00 01 2c isync
204: 48 00 00 01 bl 204 <._copy_to_user+0x54>
204: R_PPC64_REL24 .__copy_tofrom_user
...
0000000000000260 <._copy_from_user>:
...
2ec: 4c 00 01 2c isync
2f0: 39 20 ff ff li r9,-1
2f4: 79 29 00 04 rldicr r9,r9,0,0
2f8: 7d 3d 03 a6 mtspr 29,r9
2fc: 4c 00 01 2c isync
300: 7f c5 f3 78 mr r5,r30
304: 7f 83 e3 78 mr r3,r28
308: 48 00 00 01 bl 308 <._copy_from_user+0xa8>
308: R_PPC64_REL24 .__copy_tofrom_user
...
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
[mpe: Spell out the directions, s/KUAP_R/KUAP_READ/ etc.]
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/56743b700c56e5d341468151f0e95ff0c46663cd.1579715466.git.christophe.leroy@xxxxxx
---
v4: taken from powerpc/next-test
---
arch/powerpc/include/asm/book3s/32/kup.h | 13 ++++++--
.../powerpc/include/asm/book3s/64/kup-radix.h | 11 +++----
arch/powerpc/include/asm/kup.h | 30 ++++++++++++++-----
arch/powerpc/include/asm/nohash/32/kup-8xx.h | 4 +--
arch/powerpc/include/asm/uaccess.h | 4 +--
5 files changed, 43 insertions(+), 19 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index d88008c8eb85..91c8f1d9bcee 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h
@@ -102,11 +102,13 @@ static inline void kuap_update_sr(u32 sr, u32 addr, u32 end)
isync(); /* Context sync required after mtsrin() */
}
-static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
+static __always_inline void allow_user_access(void __user *to, const void __user *from,
+ u32 size, unsigned long dir)
{
u32 addr, end;
- if (__builtin_constant_p(to) && to == NULL)
+ BUILD_BUG_ON(!__builtin_constant_p(dir));
+ if (!(dir & KUAP_WRITE))
return;
addr = (__force u32)to;
@@ -119,11 +121,16 @@ static inline void allow_user_access(void __user *to, const void __user *from, u
kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
}
-static inline void prevent_user_access(void __user *to, const void __user *from, u32 size)
+static __always_inline void prevent_user_access(void __user *to, const void __user *from,
+ u32 size, unsigned long dir)
{
u32 addr = (__force u32)to;
u32 end = min(addr + size, TASK_SIZE);
+ BUILD_BUG_ON(!__builtin_constant_p(dir));
+ if (!(dir & KUAP_WRITE))
+ return;
+
if (!addr || addr >= TASK_SIZE || !size)
return;
diff --git a/arch/powerpc/include/asm/book3s/64/kup-radix.h b/arch/powerpc/include/asm/book3s/64/kup-radix.h
index dbbd22cb80f5..c8d1076e0ebb 100644
--- a/arch/powerpc/include/asm/book3s/64/kup-radix.h
+++ b/arch/powerpc/include/asm/book3s/64/kup-radix.h
@@ -77,20 +77,21 @@ static inline void set_kuap(unsigned long value)
isync();
}
-static inline void allow_user_access(void __user *to, const void __user *from,
- unsigned long size)
+static __always_inline void allow_user_access(void __user *to, const void __user *from,
+ unsigned long size, unsigned long dir)
{
// This is written so we can resolve to a single case at build time
- if (__builtin_constant_p(to) && to == NULL)
+ BUILD_BUG_ON(!__builtin_constant_p(dir));
+ if (dir == KUAP_READ)
set_kuap(AMR_KUAP_BLOCK_WRITE);
- else if (__builtin_constant_p(from) && from == NULL)
+ else if (dir == KUAP_WRITE)
set_kuap(AMR_KUAP_BLOCK_READ);
else
set_kuap(0);
}
static inline void prevent_user_access(void __user *to, const void __user *from,
- unsigned long size)
+ unsigned long size, unsigned long dir)
{
set_kuap(AMR_KUAP_BLOCKED);
}
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index 812e66f31934..94f24928916a 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h
@@ -2,6 +2,10 @@
#ifndef _ASM_POWERPC_KUP_H_
#define _ASM_POWERPC_KUP_H_
+#define KUAP_READ 1
+#define KUAP_WRITE 2
+#define KUAP_READ_WRITE (KUAP_READ | KUAP_WRITE)
+
#ifdef CONFIG_PPC64
#include <asm/book3s/64/kup-radix.h>
#endif
@@ -42,9 +46,9 @@ void setup_kuap(bool disabled);
#else
static inline void setup_kuap(bool disabled) { }
static inline void allow_user_access(void __user *to, const void __user *from,
- unsigned long size) { }
+ unsigned long size, unsigned long dir) { }
static inline void prevent_user_access(void __user *to, const void __user *from,
- unsigned long size) { }
+ unsigned long size, unsigned long dir) { }
static inline bool
bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
{
@@ -54,24 +58,36 @@ bad_kuap_fault(struct pt_regs *regs, unsigned long address, bool is_write)
static inline void allow_read_from_user(const void __user *from, unsigned long size)
{
- allow_user_access(NULL, from, size);
+ allow_user_access(NULL, from, size, KUAP_READ);
}
static inline void allow_write_to_user(void __user *to, unsigned long size)
{
- allow_user_access(to, NULL, size);
+ allow_user_access(to, NULL, size, KUAP_WRITE);
+}
+
+static inline void allow_read_write_user(void __user *to, const void __user *from,
+ unsigned long size)
+{
+ allow_user_access(to, from, size, KUAP_READ_WRITE);
}
static inline void prevent_read_from_user(const void __user *from, unsigned long size)
{
- prevent_user_access(NULL, from, size);
+ prevent_user_access(NULL, from, size, KUAP_READ);
}
static inline void prevent_write_to_user(void __user *to, unsigned long size)
{
- prevent_user_access(to, NULL, size);
+ prevent_user_access(to, NULL, size, KUAP_WRITE);
+}
+
+static inline void prevent_read_write_user(void __user *to, const void __user *from,
+ unsigned long size)
+{
+ prevent_user_access(to, from, size, KUAP_READ_WRITE);
}
#endif /* !__ASSEMBLY__ */
-#endif /* _ASM_POWERPC_KUP_H_ */
+#endif /* _ASM_POWERPC_KUAP_H_ */
diff --git a/arch/powerpc/include/asm/nohash/32/kup-8xx.h b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
index f2fea603b929..1d70c80366fd 100644
--- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h
@@ -35,13 +35,13 @@
#include <asm/reg.h>
static inline void allow_user_access(void __user *to, const void __user *from,
- unsigned long size)
+ unsigned long size, unsigned long dir)
{
mtspr(SPRN_MD_AP, MD_APG_INIT);
}
static inline void prevent_user_access(void __user *to, const void __user *from,
- unsigned long size)
+ unsigned long size, unsigned long dir)
{
mtspr(SPRN_MD_AP, MD_APG_KUAP);
}
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index c92fe7fe9692..cafad1960e76 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -313,9 +313,9 @@ raw_copy_in_user(void __user *to, const void __user *from, unsigned long n)
unsigned long ret;
barrier_nospec();
- allow_user_access(to, from, n);
+ allow_read_write_user(to, from, n);
ret = __copy_tofrom_user(to, from, n);
- prevent_user_access(to, from, n);
+ prevent_read_write_user(to, from, n);
return ret;
}
#endif /* __powerpc64__ */
--
2.25.0