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>
---
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
