From: Christophe Leroy christophe.leroy@c-s.fr
[ Upstream commit 1d8f739b07bd538f272f60bf53f10e7e6248d295 ]
__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@c-s.fr [mpe: Spell out the directions, s/KUAP_R/KUAP_READ/ etc.] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/f4e88ec4941d5facb35ce75026b0112f980086c3.157986675... Signed-off-by: Sasha Levin sashal@kernel.org --- 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 d88008c8eb852..91c8f1d9bceef 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 dbbd22cb80f5a..c8d1076e0ebbf 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 812e66f31934f..94f24928916a8 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 9d1fe811aa5d6..6fe97465e350b 100644 --- a/arch/powerpc/include/asm/nohash/32/kup-8xx.h +++ b/arch/powerpc/include/asm/nohash/32/kup-8xx.h @@ -34,13 +34,13 @@ #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 c92fe7fe9692c..cafad1960e766 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__ */