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. 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 ? Also,I searched for the functions with names that match get_dma_residue in the kernel source code and found that they return unsigned int. I also noticed that no error checks have been made to check if get_dma_residue was successful. > thanks, > > greg k-h Thanks, Everest K.C.
