liveupdate: luo_core: fix redundant bound check in luo_ioctl()

[PATCH] liveupdate: luo_core: fix redundant bound check in luo_ioctl()

Posted by Pasha Tatashin 1 day, 20 hours ago

The kernel test robot reported a Smatch warning:
kernel/liveupdate/luo_core.c:402 luo_ioctl() warn: unsigned 'nr' is
never less than zero.

This occurs because 'nr' is unsigned and LIVEUPDATE_CMD_BASE is
currently defined as 0, making the check (nr < LIVEUPDATE_CMD_BASE)
always false.

Remove the explicit lower bound check. The logic remains correct because
'nr' is unsigned; if nr is less than LIVEUPDATE_CMD_BASE, the expression
(nr - LIVEUPDATE_CMD_BASE) will wrap around to a large positive value.
This will inevitably be larger than ARRAY_SIZE(luo_ioctl_ops) and be
caught by the upper bound check.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511280300.6pvBmXUS-lkp@intel.com/
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/liveupdate/luo_core.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
index 69298d82f404..7a9ef16b37d8 100644
--- a/kernel/liveupdate/luo_core.c
+++ b/kernel/liveupdate/luo_core.c
@@ -404,10 +404,8 @@ static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
 	int err;
 
 	nr = _IOC_NR(cmd);
-	if (nr < LIVEUPDATE_CMD_BASE ||
-	    (nr - LIVEUPDATE_CMD_BASE) >= ARRAY_SIZE(luo_ioctl_ops)) {
+	if (nr - LIVEUPDATE_CMD_BASE >= ARRAY_SIZE(luo_ioctl_ops))
 		return -EINVAL;
-	}
 
 	ucmd.ubuffer = (void __user *)arg;
 	err = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);

base-commit: 7d31f578f3230f3b7b33b0930b08f9afd8429817
-- 
2.52.0.487.g5c8c507ade-goog

Re: [PATCH] liveupdate: luo_core: fix redundant bound check in luo_ioctl()

Posted by Pratyush Yadav 22 hours ago

On Sat, Nov 29 2025, Pasha Tatashin wrote:

> The kernel test robot reported a Smatch warning:
> kernel/liveupdate/luo_core.c:402 luo_ioctl() warn: unsigned 'nr' is
> never less than zero.
>
> This occurs because 'nr' is unsigned and LIVEUPDATE_CMD_BASE is
> currently defined as 0, making the check (nr < LIVEUPDATE_CMD_BASE)
> always false.
>
> Remove the explicit lower bound check. The logic remains correct because
> 'nr' is unsigned; if nr is less than LIVEUPDATE_CMD_BASE, the expression
> (nr - LIVEUPDATE_CMD_BASE) will wrap around to a large positive value.
> This will inevitably be larger than ARRAY_SIZE(luo_ioctl_ops) and be
> caught by the upper bound check.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202511280300.6pvBmXUS-lkp@intel.com/
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Reviewed-by: Pratyush Yadav <pratyush@kernel.org>

[...]

-- 
Regards,
Pratyush Yadav

Re: [PATCH] liveupdate: luo_core: fix redundant bound check in luo_ioctl()

Posted by Mike Rapoport 1 day, 11 hours ago

On Sat, Nov 29, 2025 at 08:09:19PM -0500, Pasha Tatashin wrote:
> The kernel test robot reported a Smatch warning:
> kernel/liveupdate/luo_core.c:402 luo_ioctl() warn: unsigned 'nr' is
> never less than zero.
> 
> This occurs because 'nr' is unsigned and LIVEUPDATE_CMD_BASE is
> currently defined as 0, making the check (nr < LIVEUPDATE_CMD_BASE)
> always false.
> 
> Remove the explicit lower bound check. The logic remains correct because
> 'nr' is unsigned; if nr is less than LIVEUPDATE_CMD_BASE, the expression
> (nr - LIVEUPDATE_CMD_BASE) will wrap around to a large positive value.
> This will inevitably be larger than ARRAY_SIZE(luo_ioctl_ops) and be
> caught by the upper bound check.
> 
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202511280300.6pvBmXUS-lkp@intel.com/
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>

Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  kernel/liveupdate/luo_core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/kernel/liveupdate/luo_core.c b/kernel/liveupdate/luo_core.c
> index 69298d82f404..7a9ef16b37d8 100644
> --- a/kernel/liveupdate/luo_core.c
> +++ b/kernel/liveupdate/luo_core.c
> @@ -404,10 +404,8 @@ static long luo_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  	int err;
>  
>  	nr = _IOC_NR(cmd);
> -	if (nr < LIVEUPDATE_CMD_BASE ||
> -	    (nr - LIVEUPDATE_CMD_BASE) >= ARRAY_SIZE(luo_ioctl_ops)) {
> +	if (nr - LIVEUPDATE_CMD_BASE >= ARRAY_SIZE(luo_ioctl_ops))
>  		return -EINVAL;
> -	}
>  
>  	ucmd.ubuffer = (void __user *)arg;
>  	err = get_user(ucmd.user_size, (u32 __user *)ucmd.ubuffer);
> 
> base-commit: 7d31f578f3230f3b7b33b0930b08f9afd8429817
> -- 
> 2.52.0.487.g5c8c507ade-goog
> 

-- 
Sincerely yours,
Mike.