On Thu, Nov 12, 2020 at 08:12:55PM +0100, Lukas Bulwahn wrote: > When usb_stor_bulk_transfer_sglist() returns with USB_STOR_XFER_ERROR, it > returns without writing to its parameter *act_len. > > Further, the two callers of usb_stor_bulk_transfer_sglist(): > > usb_stor_bulk_srb() and > usb_stor_bulk_transfer_sg(), > > use the passed variable partial without checking the return value. Hence, > the uninitialized value of partial is then used in the further execution > of those two functions. > > Clang-analyzer detects this potential control and data flow and warns: > > drivers/usb/storage/transport.c:469:40: > warning: The right operand of '-' is a garbage value > [clang-analyzer-core.UndefinedBinaryOperatorResult] > scsi_set_resid(srb, scsi_bufflen(srb) - partial); > ^ > > drivers/usb/storage/transport.c:495:15: > warning: Assigned value is garbage or undefined > [clang-analyzer-core.uninitialized.Assign] > length_left -= partial; > ^ > > When a transfer error occurs, the *act_len value is probably ignored by the > higher layers. But it won't hurt to set it to a valid number, just in case. > > For the two early-return paths in usb_stor_bulk_transfer_sglist(), the > amount of data transferred is 0. So if act_len is not NULL, set *act_len > to 0 in those paths. That makes clang-analyzer happy. > > Proposal was discussed in this mail thread: > > Link: https://lore.kernel.org/linux-usb/alpine.DEB.2.21.2011112146110.13119@felia/ > > Signed-off-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx> Assuming that setting it to zero is okay (sounds like it is based on the other thread), this is a reasonable fix. Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > --- > applies cleanly on current master and next-20201112 > > I did some basic compile testing... > > Alan, Greg, please pick this minor non-urgent clean-up patch. > > drivers/usb/storage/transport.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c > index 238a8088e17f..5eb895b19c55 100644 > --- a/drivers/usb/storage/transport.c > +++ b/drivers/usb/storage/transport.c > @@ -416,7 +416,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe, > > /* don't submit s-g requests during abort processing */ > if (test_bit(US_FLIDX_ABORTING, &us->dflags)) > - return USB_STOR_XFER_ERROR; > + goto usb_stor_xfer_error; > > /* initialize the scatter-gather request block */ > usb_stor_dbg(us, "xfer %u bytes, %d entries\n", length, num_sg); > @@ -424,7 +424,7 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe, > sg, num_sg, length, GFP_NOIO); > if (result) { > usb_stor_dbg(us, "usb_sg_init returned %d\n", result); > - return USB_STOR_XFER_ERROR; > + goto usb_stor_xfer_error; > } > > /* > @@ -452,6 +452,11 @@ static int usb_stor_bulk_transfer_sglist(struct us_data *us, unsigned int pipe, > *act_len = us->current_sg.bytes; > return interpret_urb_result(us, pipe, length, result, > us->current_sg.bytes); > + > +usb_stor_xfer_error: > + if (act_len) > + *act_len = 0; > + return USB_STOR_XFER_ERROR; > } > > /* > -- > 2.17.1 >
