[linux-stable-rc:linux-4.4.y 1449/1774] drivers/input/joydev.c:485:16: warning: comparison of integer expressions of different signedness: 'int' and 'long unsigned int'
1:39 p.m.
tree: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
linux-4.4.y
head: 38c92ba3580f0d00e57a55caf8f880aa1a0f2a50
commit: ade5180681d778d36b569ad35cc175ab22196c5f [1449/1774] Input: joydev - prevent
potential read overflow in ioctl
config: h8300-randconfig-r031-20210718 (attached as .config)
compiler: h8300-linux-gcc (GCC) 10.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O
~/bin/make.cross
chmod +x ~/bin/make.cross
#
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.gi...
git remote add linux-stable-rc
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
git fetch --no-tags linux-stable-rc linux-4.4.y
git checkout ade5180681d778d36b569ad35cc175ab22196c5f
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross ARCH=h8300
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp(a)intel.com>
All warnings (new ones prefixed by >>):
In file included from arch/h8300/include/generated/asm/uaccess.h:1,
from include/linux/poll.h:11,
from drivers/input/joydev.c:27:
include/asm-generic/uaccess.h: In function '__put_user_fn':
include/asm-generic/uaccess.h:178:16: warning: operand of '?:' changes
signedness from 'int' to 'size_t' {aka 'long unsigned int'} due to
unsignedness of other operand [-Wsign-compare]
178 | return size ? -EFAULT : size;
drivers/input/joydev.c: In function 'joydev_handle_JSIOCSAXMAP':
drivers/input/joydev.c:451:16: warning: comparison of integer expressions of different
signedness: 'int' and 'size_t' {aka 'long unsigned int'}
[-Wsign-compare]
451 | for (i = 0; i < len && i < joydev->nabs; i++) {
| ^
drivers/input/joydev.c: In function 'joydev_handle_JSIOCSBTNMAP':
> drivers/input/joydev.c:485:16: warning: comparison of integer
expressions of different signedness: 'int' and 'long unsigned int'
[-Wsign-compare]
485 | for (i = 0; i < (len / 2) && i <
joydev->nkey; i++) {
| ^
drivers/input/joydev.c: In function 'joydev_ioctl_common':
drivers/input/joydev.c:566:52: warning: operand of '?:' changes signedness from
'int' to 'size_t' {aka 'long unsigned int'} due to unsignedness of
other operand [-Wsign-compare]
566 | return copy_to_user(argp, joydev->abspam, len) ? -EFAULT : len;
drivers/input/joydev.c:573:52: warning: operand of '?:' changes signedness from
'int' to 'size_t' {aka 'long unsigned int'} due to unsignedness of
other operand [-Wsign-compare]
573 | return copy_to_user(argp, joydev->keypam, len) ? -EFAULT : len;
drivers/input/joydev.c:581:42: warning: operand of '?:' changes signedness from
'int' to 'size_t' {aka 'long unsigned int'} due to unsignedness of
other operand [-Wsign-compare]
581 | return copy_to_user(argp, name, len) ? -EFAULT : len;
vim +485 drivers/input/joydev.c
467
468 static int joydev_handle_JSIOCSBTNMAP(struct joydev *joydev,
469 void __user *argp, size_t len)
470 {
471 __u16 *keypam;
472 int i;
473 int retval = 0;
474
475 if (len % sizeof(*keypam))
476 return -EINVAL;
477
478 len = min(len, sizeof(joydev->keypam));
479
480 /* Validate the map. */
481 keypam = memdup_user(argp, len);
482 if (IS_ERR(keypam))
483 return PTR_ERR(keypam);
484
485 for (i = 0; i < (len / 2) && i < joydev->nkey;
i++) {
486 if (keypam[i] > KEY_MAX || keypam[i] < BTN_MISC) {
487 retval = -EINVAL;
488 goto out;
489 }
490 }
491
492 memcpy(joydev->keypam, keypam, len);
493
494 for (i = 0; i < joydev->nkey; i++)
495 joydev->keymap[keypam[i] - BTN_MISC] = i;
496
497 out:
498 kfree(keypam);
499 return retval;
500 }
501
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
5:17 p.m.
On Mon, Jul 19, 2021 at 11:39:16AM +0800, kernel test robot wrote:
drivers/input/joydev.c: In function
'joydev_handle_JSIOCSAXMAP':
drivers/input/joydev.c:451:16: warning: comparison of integer expressions of different
signedness: 'int' and 'size_t' {aka 'long unsigned int'}
[-Wsign-compare]
451 | for (i = 0; i < len && i < joydev->nabs; i++) {
We should figure out a way to turn this warning off in the compiler.
It's a stupid warning. It never fixes any bugs. It sometimes
introduces bugs.
In the kernel if you are in drivers/ and you have a loop which iterates
over 2 million times that's probably a bug. But GCC is very very
stupid and not designed to be a static analysis tool. It does not know
which loops can iterate more than 2 million times. Even when it knows
that the loop only loops up to 5 or 10 times it still warns that maybe
it will loop over 2 million times. INSULTS AND DISPARAGEMENT!
Seriously, please disable this warning unless you can point to one
single bug that it has fixed.
regards,
dan carpenter
6:46 p.m.
On 7/19/21 3:17 PM, Dan Carpenter wrote:
On Mon, Jul 19, 2021 at 11:39:16AM +0800, kernel test robot wrote:
> drivers/input/joydev.c: In function 'joydev_handle_JSIOCSAXMAP':
> drivers/input/joydev.c:451:16: warning: comparison of integer expressions of
different signedness: 'int' and 'size_t' {aka 'long unsigned int'}
[-Wsign-compare]
> 451 | for (i = 0; i < len && i < joydev->nabs; i++) {
We should figure out a way to turn this warning off in the compiler.
It's a stupid warning. It never fixes any bugs. It sometimes
introduces bugs.
In the kernel if you are in drivers/ and you have a loop which iterates
over 2 million times that's probably a bug. But GCC is very very
stupid and not designed to be a static analysis tool. It does not know
which loops can iterate more than 2 million times. Even when it knows
that the loop only loops up to 5 or 10 times it still warns that maybe
it will loop over 2 million times. INSULTS AND DISPARAGEMENT!
Seriously, please disable this warning unless you can point to one
single bug that it has fixed.
Hi Dan,
Thanks for the explanation, we'll stop reporting this warning.
Best Regards,
Rong Chen
regards,
dan carpenter
428
days inactive
428
days old
2 comments
3 participants
participants (3)
-
Dan Carpenter -
kernel test robot -
Rong Chen