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53f01e2004
commit 4012e77a90 upstream.
A NMI can hit in the middle of context switching or in the middle of
switch_mm_irqs_off(). In either case, CR3 might not match current->mm,
which could cause copy_from_user_nmi() and friends to read the wrong
memory.
Fix it by adding a new nmi_uaccess_okay() helper and checking it in
copy_from_user_nmi() and in __copy_from_user_nmi()'s callers.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jann Horn <jannh@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/dd956eba16646fd0b15c3c0741269dfd84452dac.1535557289.git.luto@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
39 lines
845 B
C
39 lines
845 B
C
/*
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* User address space access functions.
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*
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* For licencing details see kernel-base/COPYING
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*/
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#include <linux/uaccess.h>
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#include <linux/export.h>
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#include <asm/tlbflush.h>
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/*
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* We rely on the nested NMI work to allow atomic faults from the NMI path; the
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* nested NMI paths are careful to preserve CR2.
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*/
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unsigned long
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copy_from_user_nmi(void *to, const void __user *from, unsigned long n)
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{
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unsigned long ret;
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if (__range_not_ok(from, n, TASK_SIZE))
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return n;
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if (!nmi_uaccess_okay())
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return n;
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/*
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* Even though this function is typically called from NMI/IRQ context
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* disable pagefaults so that its behaviour is consistent even when
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* called form other contexts.
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*/
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pagefault_disable();
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ret = __copy_from_user_inatomic(to, from, n);
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pagefault_enable();
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return ret;
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}
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EXPORT_SYMBOL_GPL(copy_from_user_nmi);
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