From: Andrew Donnellan ajd@linux.ibm.com
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 dja@axtens.net Suggested-by: Michael Ellerman mpe@ellerman.id.au Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection") Signed-off-by: Andrew Donnellan ajd@linux.ibm.com [mpe: Use __arch_clear_user() for the asm version like arm64 & nds32] Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com Signed-off-by: Daniel Axtens dja@axtens.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/include/asm/uaccess.h | 9 +++++++-- arch/powerpc/kernel/ppc_ksyms.c | 3 +++ arch/powerpc/lib/string.S | 2 +- arch/powerpc/lib/string_64.S | 4 ++-- 4 files changed, 13 insertions(+), 5 deletions(-)
--- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -471,7 +471,7 @@ static inline unsigned long __copy_to_us 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) { @@ -479,12 +479,17 @@ static inline unsigned long clear_user(v 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); --- a/arch/powerpc/kernel/ppc_ksyms.c +++ b/arch/powerpc/kernel/ppc_ksyms.c @@ -5,6 +5,7 @@ #include <asm/switch_to.h> #include <asm/cacheflush.h> #include <asm/epapr_hcalls.h> +#include <asm/uaccess.h>
EXPORT_SYMBOL(flush_dcache_range); EXPORT_SYMBOL(flush_icache_range); @@ -43,3 +44,5 @@ EXPORT_SYMBOL(epapr_hypercall_start); #endif
EXPORT_SYMBOL(current_stack_pointer); + +EXPORT_SYMBOL(__arch_clear_user); --- a/arch/powerpc/lib/string.S +++ b/arch/powerpc/lib/string.S @@ -122,7 +122,7 @@ _GLOBAL(memchr) blr
#ifdef CONFIG_PPC32 -_GLOBAL(__clear_user) +_GLOBAL(__arch_clear_user) addi r6,r3,-4 li r3,0 li r5,0 --- a/arch/powerpc/lib/string_64.S +++ b/arch/powerpc/lib/string_64.S @@ -27,7 +27,7 @@ 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. * @@ -77,7 +77,7 @@ 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