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powerpc: Fix __clear_user() with KUAP enabled
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: de78a9c42a
("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
This commit is contained in:
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@ -401,7 +401,7 @@ copy_to_user_mcsafe(void __user *to, const void *from, unsigned long n)
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return n;
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}
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extern unsigned long __clear_user(void __user *addr, unsigned long size);
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unsigned long __arch_clear_user(void __user *addr, unsigned long size);
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static inline unsigned long clear_user(void __user *addr, unsigned long size)
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{
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@ -409,12 +409,17 @@ static inline unsigned long clear_user(void __user *addr, unsigned long size)
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might_fault();
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if (likely(access_ok(addr, size))) {
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allow_write_to_user(addr, size);
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ret = __clear_user(addr, size);
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ret = __arch_clear_user(addr, size);
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prevent_write_to_user(addr, size);
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}
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return ret;
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}
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static inline unsigned long __clear_user(void __user *addr, unsigned long size)
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{
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return clear_user(addr, size);
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}
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extern long strncpy_from_user(char *dst, const char __user *src, long count);
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extern __must_check long strnlen_user(const char __user *str, long n);
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@ -17,7 +17,7 @@ CACHELINE_BYTES = L1_CACHE_BYTES
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LG_CACHELINE_BYTES = L1_CACHE_SHIFT
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CACHELINE_MASK = (L1_CACHE_BYTES-1)
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_GLOBAL(__clear_user)
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_GLOBAL(__arch_clear_user)
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/*
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* Use dcbz on the complete cache lines in the destination
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* to set them to zero. This requires that the destination
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@ -87,4 +87,4 @@ _GLOBAL(__clear_user)
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EX_TABLE(8b, 91b)
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EX_TABLE(9b, 91b)
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EXPORT_SYMBOL(__clear_user)
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EXPORT_SYMBOL(__arch_clear_user)
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@ -17,7 +17,7 @@ PPC64_CACHES:
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.section ".text"
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/**
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* __clear_user: - Zero a block of memory in user space, with less checking.
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* __arch_clear_user: - Zero a block of memory in user space, with less checking.
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* @to: Destination address, in user space.
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* @n: Number of bytes to zero.
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*
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@ -58,7 +58,7 @@ err3; stb r0,0(r3)
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mr r3,r4
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blr
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_GLOBAL_TOC(__clear_user)
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_GLOBAL_TOC(__arch_clear_user)
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cmpdi r4,32
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neg r6,r3
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li r0,0
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@ -181,4 +181,4 @@ err1; dcbz 0,r3
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cmpdi r4,32
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blt .Lshort_clear
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b .Lmedium_clear
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EXPORT_SYMBOL(__clear_user)
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EXPORT_SYMBOL(__arch_clear_user)
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