78 lines
2.8 KiB
Diff
78 lines
2.8 KiB
Diff
From: Dan Williams <dan.j.williams@intel.com>
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Date: Fri, 16 Feb 2018 13:20:42 -0800
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Subject: nospec: Kill array_index_nospec_mask_check()
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Origin: https://git.kernel.org/linus/1d91c1d2c80cb70e2e553845e278b87a960c04da
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There are multiple problems with the dynamic sanity checking in
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array_index_nospec_mask_check():
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* It causes unnecessary overhead in the 32-bit case since integer sized
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@index values will no longer cause the check to be compiled away like
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in the 64-bit case.
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* In the 32-bit case it may trigger with user controllable input when
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the expectation is that should only trigger during development of new
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kernel enabling.
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* The macro reuses the input parameter in multiple locations which is
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broken if someone passes an expression like 'index++' to
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array_index_nospec().
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Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
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Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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Cc: Andy Lutomirski <luto@kernel.org>
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Cc: Arjan van de Ven <arjan@linux.intel.com>
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Cc: Borislav Petkov <bp@alien8.de>
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Cc: Dave Hansen <dave.hansen@linux.intel.com>
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Cc: David Woodhouse <dwmw2@infradead.org>
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Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Cc: Josh Poimboeuf <jpoimboe@redhat.com>
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Cc: Peter Zijlstra <peterz@infradead.org>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: Will Deacon <will.deacon@arm.com>
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Cc: linux-arch@vger.kernel.org
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Link: http://lkml.kernel.org/r/151881604278.17395.6605847763178076520.stgit@dwillia2-desk3.amr.corp.intel.com
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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---
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include/linux/nospec.h | 22 +---------------------
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1 file changed, 1 insertion(+), 21 deletions(-)
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--- a/include/linux/nospec.h
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+++ b/include/linux/nospec.h
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@@ -30,26 +30,6 @@ static inline unsigned long array_index_
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#endif
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/*
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- * Warn developers about inappropriate array_index_nospec() usage.
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- *
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- * Even if the CPU speculates past the WARN_ONCE branch, the
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- * sign bit of @index is taken into account when generating the
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- * mask.
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- *
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- * This warning is compiled out when the compiler can infer that
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- * @index and @size are less than LONG_MAX.
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- */
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-#define array_index_mask_nospec_check(index, size) \
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-({ \
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- if (WARN_ONCE(index > LONG_MAX || size > LONG_MAX, \
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- "array_index_nospec() limited to range of [0, LONG_MAX]\n")) \
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- _mask = 0; \
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- else \
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- _mask = array_index_mask_nospec(index, size); \
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- _mask; \
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-})
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-
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-/*
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* array_index_nospec - sanitize an array index after a bounds check
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*
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* For a code sequence like:
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@@ -67,7 +47,7 @@ static inline unsigned long array_index_
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({ \
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typeof(index) _i = (index); \
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typeof(size) _s = (size); \
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- unsigned long _mask = array_index_mask_nospec_check(_i, _s); \
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+ unsigned long _mask = array_index_mask_nospec(_i, _s); \
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\
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BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
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BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
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