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[2001:44b8:1113:6700:4d44:522c:3789:8f33]) by smtp.gmail.com with ESMTPSA id fh22sm908796pjb.45.2020.11.19.15.58.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Nov 2020 15:58:08 -0800 (PST) From: Daniel Axtens To: stable@vger.kernel.org Cc: dja@axtens.net Subject: [PATCH 4.9 6/8] powerpc: Fix __clear_user() with KUAP enabled Date: Fri, 20 Nov 2020 10:57:41 +1100 Message-Id: <20201119235743.373635-7-dja@axtens.net> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201119235743.373635-1-dja@axtens.net> References: <20201119235743.373635-1-dja@axtens.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Andrew Donnellan commit 61e3acd8c693a14fc69b824cb5b08d02cb90a6e7 upstream. The KUAP implementation adds calls in clear_user() to enable and disable access to userspace memory. However, it doesn't add these to __clear_user(), which is used in the ptrace regset code. As there's only one direct user of __clear_user() (the regset code), and the time taken to set the AMR for KUAP purposes is going to dominate the cost of a quick access_ok(), there's not much point having a separate path. Rename __clear_user() to __arch_clear_user(), and make __clear_user() just call clear_user(). Reported-by: syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com Reported-by: Daniel Axtens Suggested-by: Michael Ellerman Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan [mpe: Use __arch_clear_user() for the asm version like arm64 & nds32] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com Signed-off-by: Daniel Axtens --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/lib/string.S | 4 ++-- arch/powerpc/lib/string_64.S | 6 +++--- 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index a395e440c320..5fc6a9f410f2 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -460,7 +460,7 @@ static inline unsigned long __copy_to_user(void __user *to, return __copy_to_user_inatomic(to, from, size); } -extern unsigned long __clear_user(void __user *addr, unsigned long size); +unsigned long __arch_clear_user(void __user *addr, unsigned long size); static inline unsigned long clear_user(void __user *addr, unsigned long size) { @@ -468,12 +468,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size) might_fault(); if (likely(access_ok(VERIFY_WRITE, addr, size))) { allow_write_to_user(addr, size); - ret = __clear_user(addr, size); + ret = __arch_clear_user(addr, size); prevent_write_to_user(addr, size); } return ret; } +static inline unsigned long __clear_user(void __user *addr, unsigned long size) +{ + return clear_user(addr, size); +} + extern long strncpy_from_user(char *dst, const char __user *src, long count); extern __must_check long strlen_user(const char __user *str); extern __must_check long strnlen_user(const char __user *str, long n); diff --git a/arch/powerpc/lib/string.S b/arch/powerpc/lib/string.S index d13e07603519..4e85411d4a7e 100644 --- a/arch/powerpc/lib/string.S +++ b/arch/powerpc/lib/string.S @@ -89,7 +89,7 @@ _GLOBAL(memchr) EXPORT_SYMBOL(memchr) #ifdef CONFIG_PPC32 -_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) addi r6,r3,-4 li r3,0 li r5,0 @@ -130,5 +130,5 @@ _GLOBAL(__clear_user) PPC_LONG 1b,91b PPC_LONG 8b,92b .text -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user) #endif diff --git a/arch/powerpc/lib/string_64.S b/arch/powerpc/lib/string_64.S index 11e6372537fd..347029f65edb 100644 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -28,7 +28,7 @@ PPC64_CACHES: .section ".text" /** - * __clear_user: - Zero a block of memory in user space, with less checking. + * __arch_clear_user: - Zero a block of memory in user space, with less checking. * @to: Destination address, in user space. * @n: Number of bytes to zero. * @@ -78,7 +78,7 @@ err3; stb r0,0(r3) mr r3,r4 blr -_GLOBAL_TOC(__clear_user) +_GLOBAL_TOC(__arch_clear_user) cmpdi r4,32 neg r6,r3 li r0,0 @@ -201,4 +201,4 @@ err1; dcbz 0,r3 cmpdi r4,32 blt .Lshort_clear b .Lmedium_clear -EXPORT_SYMBOL(__clear_user) +EXPORT_SYMBOL(__arch_clear_user)