Hi Dan, On Thu, Nov 16, 2017 at 06:09:20PM -0500, Dan Gopstein wrote: > From: Dan Gopstein <dgopstein@xxxxxxx> > > Two definitions of the ABS (absolute value) macro fail to parenthesize their > parameter properly. This can lead to a bad expansion for low-precedence > expression arguments. Add parens to protect against troublesome arguments. > > Signed-off-by: Dan Gopstein <dgopstein@xxxxxxx> > --- > See an example bad usage in > drivers/media/dvb-frontends/mb86a16.c b/drivers/media/dvb-frontends/mb86a16.c > on line 1204: > > ABS(prev_swp_freq[j] - swp_freq) > > For example: ABS(1-2) currently expands to ((1-2) < 0 ? (-1-2) : (1-2)) which > evaluates to -3. But the correct expansion would be ((1-2) < 0 ? -(1-2) : (1-2)) > which evaluates to 1. This example would be nice to have in the commit log. > I found this issue as part of the "Atoms of Confusion" research at NYU's Secure > Systems Lab. As the work continues, hopefully we'll be able to find more issues > like this one. > > diff --git a/drivers/media/dvb-frontends/dibx000_common.h > b/drivers/media/dvb-frontends/dibx000_common.h Unfortunately, your email client (gmail?) mangled the patch by splitting lines like the above. So 'git am', or the 'patch' utility can't apply your patch as is. I suggest you to use 'git send-email' to send patches. You can find gmail specific setup instructions in the git-send-email man page[1] under EXAMPLE. [1] https://git-scm.com/docs/git-send-email baruch > index 8784af9..ae60f5d 100644 > --- a/drivers/media/dvb-frontends/dibx000_common.h > +++ b/drivers/media/dvb-frontends/dibx000_common.h > @@ -223,7 +223,7 @@ struct dvb_frontend_parametersContext { > > #define FE_CALLBACK_TIME_NEVER 0xffffffff > > -#define ABS(x) ((x < 0) ? (-x) : (x)) > +#define ABS(x) (((x) < 0) ? -(x) : (x)) > > #define DATA_BUS_ACCESS_MODE_8BIT 0x01 > #define DATA_BUS_ACCESS_MODE_16BIT 0x02 > diff --git a/drivers/media/dvb-frontends/mb86a16.c > b/drivers/media/dvb-frontends/mb86a16.c > index dfe322e..2d921c7 100644 > --- a/drivers/media/dvb-frontends/mb86a16.c > +++ b/drivers/media/dvb-frontends/mb86a16.c > @@ -31,7 +31,7 @@ > static unsigned int verbose = 5; > module_param(verbose, int, 0644); > > -#define ABS(x) ((x) < 0 ? (-x) : (x)) > +#define ABS(x) ((x) < 0 ? -(x) : (x)) > > struct mb86a16_state { > struct i2c_adapter *i2c_adap; -- http://baruch.siach.name/blog/ ~. .~ Tk Open Systems =}------------------------------------------------ooO--U--Ooo------------{= - baruch@xxxxxxxxxx - tel: +972.52.368.4656, http://www.tkos.co.il -
