This is a note to let you know that I've just added the patch titled
nospec: Allow index argument to have const-qualified type
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nospec-allow-index-argument-to-have-const-qualified-type.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b98c6a160a057d5686a8c54c79cc6c8c94a7d0c8 Mon Sep 17 00:00:00 2001
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Date: Fri, 16 Feb 2018 13:20:48 -0800
Subject: nospec: Allow index argument to have const-qualified type
From: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
commit b98c6a160a057d5686a8c54c79cc6c8c94a7d0c8 upstream.
The last expression in a statement expression need not be a bare
variable, quoting gcc docs
The last thing in the compound statement should be an expression
followed by a semicolon; the value of this subexpression serves as the
value of the entire construct.
and we already use that in e.g. the min/max macros which end with a
ternary expression.
This way, we can allow index to have const-qualified type, which will in
some cases avoid the need for introducing a local copy of index of
non-const qualified type. That, in turn, can prevent readers not
familiar with the internals of array_index_nospec from wondering about
the seemingly redundant extra variable, and I think that's worthwhile
considering how confusing the whole _nospec business is.
The expression _i&_mask has type unsigned long (since that is the type
of _mask, and the BUILD_BUG_ONs guarantee that _i will get promoted to
that), so in order not to change the type of the whole expression, add
a cast back to typeof(_i).
Signed-off-by: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Acked-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: David Woodhouse <dwmw2@xxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/151881604837.17395.10812767547837568328.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/nospec.h | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/include/linux/nospec.h
+++ b/include/linux/nospec.h
@@ -72,7 +72,6 @@ static inline unsigned long array_index_
BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
\
- _i &= _mask; \
- _i; \
+ (typeof(_i)) (_i & _mask); \
})
#endif /* _LINUX_NOSPEC_H */
Patches currently in stable-queue which might be from linux@xxxxxxxxxxxxxxxxxx are
queue-4.9/nospec-allow-index-argument-to-have-const-qualified-type.patch