| From ef4d6f6b275c498f8e5626c99dbeefdc5027f843 Mon Sep 17 00:00:00 2001 |
| From: Rasmus Villemoes <linux@rasmusvillemoes.dk> |
| Date: Tue, 14 May 2019 15:43:27 -0700 |
| Subject: include/linux/bitops.h: sanitize rotate primitives |
| |
| From: Rasmus Villemoes <linux@rasmusvillemoes.dk> |
| |
| commit ef4d6f6b275c498f8e5626c99dbeefdc5027f843 upstream. |
| |
| The ror32 implementation (word >> shift) | (word << (32 - shift) has |
| undefined behaviour if shift is outside the [1, 31] range. Similarly |
| for the 64 bit variants. Most callers pass a compile-time constant |
| (naturally in that range), but there's an UBSAN report that these may |
| actually be called with a shift count of 0. |
| |
| Instead of special-casing that, we can make them DTRT for all values of |
| shift while also avoiding UB. For some reason, this was already partly |
| done for rol32 (which was well-defined for [0, 31]). gcc 8 recognizes |
| these patterns as rotates, so for example |
| |
| __u32 rol32(__u32 word, unsigned int shift) |
| { |
| return (word << (shift & 31)) | (word >> ((-shift) & 31)); |
| } |
| |
| compiles to |
| |
| 0000000000000020 <rol32>: |
| 20: 89 f8 mov %edi,%eax |
| 22: 89 f1 mov %esi,%ecx |
| 24: d3 c0 rol %cl,%eax |
| 26: c3 retq |
| |
| Older compilers unfortunately do not do as well, but this only affects |
| the small minority of users that don't pass constants. |
| |
| Due to integer promotions, ro[lr]8 were already well-defined for shifts |
| in [0, 8], and ro[lr]16 were mostly well-defined for shifts in [0, 16] |
| (only mostly - u16 gets promoted to _signed_ int, so if bit 15 is set, |
| word << 16 is undefined). For consistency, update those as well. |
| |
| Link: http://lkml.kernel.org/r/20190410211906.2190-1-linux@rasmusvillemoes.dk |
| Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> |
| Reported-by: Ido Schimmel <idosch@mellanox.com> |
| Tested-by: Ido Schimmel <idosch@mellanox.com> |
| Reviewed-by: Will Deacon <will.deacon@arm.com> |
| Cc: Vadim Pasternak <vadimp@mellanox.com> |
| Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> |
| Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com> |
| Cc: Pavel Machek <pavel@ucw.cz> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Matthias Kaehlcke <mka@chromium.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/linux/bitops.h | 16 ++++++++-------- |
| 1 file changed, 8 insertions(+), 8 deletions(-) |
| |
| --- a/include/linux/bitops.h |
| +++ b/include/linux/bitops.h |
| @@ -60,7 +60,7 @@ static __always_inline unsigned long hwe |
| */ |
| static inline __u64 rol64(__u64 word, unsigned int shift) |
| { |
| - return (word << shift) | (word >> (64 - shift)); |
| + return (word << (shift & 63)) | (word >> ((-shift) & 63)); |
| } |
| |
| /** |
| @@ -70,7 +70,7 @@ static inline __u64 rol64(__u64 word, un |
| */ |
| static inline __u64 ror64(__u64 word, unsigned int shift) |
| { |
| - return (word >> shift) | (word << (64 - shift)); |
| + return (word >> (shift & 63)) | (word << ((-shift) & 63)); |
| } |
| |
| /** |
| @@ -80,7 +80,7 @@ static inline __u64 ror64(__u64 word, un |
| */ |
| static inline __u32 rol32(__u32 word, unsigned int shift) |
| { |
| - return (word << shift) | (word >> ((-shift) & 31)); |
| + return (word << (shift & 31)) | (word >> ((-shift) & 31)); |
| } |
| |
| /** |
| @@ -90,7 +90,7 @@ static inline __u32 rol32(__u32 word, un |
| */ |
| static inline __u32 ror32(__u32 word, unsigned int shift) |
| { |
| - return (word >> shift) | (word << (32 - shift)); |
| + return (word >> (shift & 31)) | (word << ((-shift) & 31)); |
| } |
| |
| /** |
| @@ -100,7 +100,7 @@ static inline __u32 ror32(__u32 word, un |
| */ |
| static inline __u16 rol16(__u16 word, unsigned int shift) |
| { |
| - return (word << shift) | (word >> (16 - shift)); |
| + return (word << (shift & 15)) | (word >> ((-shift) & 15)); |
| } |
| |
| /** |
| @@ -110,7 +110,7 @@ static inline __u16 rol16(__u16 word, un |
| */ |
| static inline __u16 ror16(__u16 word, unsigned int shift) |
| { |
| - return (word >> shift) | (word << (16 - shift)); |
| + return (word >> (shift & 15)) | (word << ((-shift) & 15)); |
| } |
| |
| /** |
| @@ -120,7 +120,7 @@ static inline __u16 ror16(__u16 word, un |
| */ |
| static inline __u8 rol8(__u8 word, unsigned int shift) |
| { |
| - return (word << shift) | (word >> (8 - shift)); |
| + return (word << (shift & 7)) | (word >> ((-shift) & 7)); |
| } |
| |
| /** |
| @@ -130,7 +130,7 @@ static inline __u8 rol8(__u8 word, unsig |
| */ |
| static inline __u8 ror8(__u8 word, unsigned int shift) |
| { |
| - return (word >> shift) | (word << (8 - shift)); |
| + return (word >> (shift & 7)) | (word << ((-shift) & 7)); |
| } |
| |
| /** |