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Commit d765c7b3 authored by Andrew Donnellan's avatar Andrew Donnellan Committed by Greg Kroah-Hartman
Browse files

powerpc: Fix __clear_user() with KUAP enabled 



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: default avatar <syzbot+f25ecf4b2982d8c7a640@syzkaller-ppc64.appspotmail.com>
Reported-by: default avatarDaniel Axtens <dja@axtens.net>
Suggested-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Fixes: de78a9c42a79 ("powerpc: Add a framework for Kernel Userspace Access Protection")
Signed-off-by: default avatarAndrew Donnellan <ajd@linux.ibm.com>
[mpe: Use __arch_clear_user() for the asm version like arm64 & nds32]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191209132221.15328-1-ajd@linux.ibm.com


Signed-off-by: default avatarDaniel Axtens <dja@axtens.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 3853ff57

arch/powerpc/include/asm/uaccess.h

+7 −2
Original line number Diff line number Diff line
@@ -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);

arch/powerpc/lib/string.S

+2 −2
Original line number Diff line number Diff line
@@ -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

arch/powerpc/lib/string_64.S

+3 −3
Original line number Diff line number Diff line
@@ -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)