On Sun 2019-04-07 09:17:39, Vadim Pasternak wrote:
>
>
> > -----Original Message-----
> > From: Pavel Machek <pavel@xxxxxx>
> > Sent: Sunday, April 07, 2019 11:46 AM
> > To: Vadim Pasternak <vadimp@xxxxxxxxxxxx>
> > Cc: jacek.anaszewski@xxxxxxxxx; linux-leds@xxxxxxxxxxxxxxx; Ido Schimmel
> > <idosch@xxxxxxxxxxxx>
> > Subject: Re: [PATCH v1 led] leds: mlxreg: Fix UBSAN warning
> >
> > On Sun 2019-04-07 07:59:01, Vadim Pasternak wrote:
> > > Fix the following UBSAN warning, reported undefined behavior at call
> > > to
> > > ror32():
> > > [ 11.426543] UBSAN: Undefined behaviour in ./include/linux/bitops.h:93:33
> > ...
> > > The warning is caused by call to ror32(), if the second parameters of
> > > this function "shift" is zero. In such case UBSAN reports the warning
> > > for the next expression: (word << (32 - shift).
> > > Fix adds validation of this parameter ? in case it?s equal zero, no
> > > need to call rotation function, since value should stay the same.
> > >
> > > Fixes: 386570d76f2f ("leds: add driver for support Mellanox regmap
> > > LEDs for BMC and x86 platform")
> > > Reported-by: Ido Schimmel <idosch@xxxxxxxxxxxx>
> > > Signed-off-by: Vadim Pasternak <vadimp@xxxxxxxxxxxx>
> >
> > Actually, rotating zero bits seems pretty valid operation. Could we get that fixed,
> > instead?
>
> Hi Pavel,
Please fix it as:
> UBSAN warns in case of call ror32(x, 0):
> static inline __u32 ror32(__u32 word, __u32 shift)
> {
+ if (!shift) return word;
> return (word >> shift) | (word << (32 - shift));
> }
>
> The ror32() shift parameter zero causes rotation right of 32
> for u32 type.
>
> For example UBSAN will produce the warning for the below code:
> u32 value = <some value>;
> value <<= 32;
Thanks,
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Attachment:
signature.asc
Description: Digital signature
