On Wed, Oct 16, 2024 at 06:54:00AM -0600, Everest K.C. wrote: > On Wed, Oct 16, 2024 at 2:04 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Wed, Oct 16, 2024 at 01:53:18AM -0600, Everest K.C. wrote: > > > The variable `residue` is an unsigned int, also the function > > > `fluke_get_dma_residue` returns an unsigned int. The value of > > > an unsigned int can only be 0 at minimum. > > > The less-than-zero comparison can never be true. > > > Fix it by removing the dead condition in the if statement. > > > > > > This issue was reported by Coverity Scan. > > > Report: > > > CID 1600782: (#1 of 1): Macro compares unsigned to 0 (NO_EFFECT) > > > unsigned_compare: This less-than-zero comparison of an unsigned value > > > is never true. residue < 0U. > > > > > > Signed-off-by: Everest K.C. <everestkc@xxxxxxxxxxxxxxxx> > > > --- > > > V1 -> V2: - Fixed typo of comparison in changelog > > > - Removed Fixes tag > > > > > > drivers/staging/gpib/eastwood/fluke_gpib.c | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c > > > index f9f149db222d..51b4f9891a34 100644 > > > --- a/drivers/staging/gpib/eastwood/fluke_gpib.c > > > +++ b/drivers/staging/gpib/eastwood/fluke_gpib.c > > > @@ -644,7 +644,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer, > > > */ > > > usleep_range(10, 15); > > > residue = fluke_get_dma_residue(e_priv->dma_channel, dma_cookie); > > > - if (WARN_ON_ONCE(residue > length || residue < 0)) > > > + if (WARN_ON_ONCE(residue > length)) > > > > No, this is incorrect, now we never notice is the call to > > fluke_get_dma_residue() has failed. Please fix that bug instead (hint, > > Covertity is giving you a pointer to where something might be wrong, but > > this change is NOT how to fix it.) > I need a little guidance here. > My best guess to fix the bug would be to make fluke_get_dma_residue() > return an int instead of unsigned int or size_t. But theoretically the > maximum value of residue can be UINT_MAX, and casting it to int will > result in a negative number, which in turn will cause the error check > condition to evaluate to true. Look at the code to see what it does. > The best solution I see would be to make fluke_get_dma_residue() return > an int (-1 for error and 0 for success). Then pass the address of residue > reference to fluke_get_dma_residue() to be updated. > Am I on the right track ? Close, yes. "-1" is not a valid error, so that needs to be fixed at the least here, as it's obviously not returning an error that gets caught today :) good luck! greg k-h
