* [PATCH] s390/hmcdrv: Replace kmalloc() + copy_from_user() with memdup_user_nul()
@ 2025-09-05 11:02 Thorsten Blum
2025-09-08 11:50 ` Alexander Gordeev
0 siblings, 1 reply; 2+ messages in thread
From: Thorsten Blum @ 2025-09-05 11:02 UTC (permalink / raw)
To: Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger, Sven Schnelle, Jan Kara, Thorsten Blum,
Christian Brauner, Jeff Layton
Cc: linux-s390, linux-kernel
Replace kmalloc() followed by copy_from_user() with memdup_user_nul() to
improve and simplify hmcdrv_dev_write(). Remove the manual
NUL-termination.
No functional changes intended.
Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
---
drivers/s390/char/hmcdrv_dev.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)
diff --git a/drivers/s390/char/hmcdrv_dev.c b/drivers/s390/char/hmcdrv_dev.c
index e069dd685899..b26fcf6849f2 100644
--- a/drivers/s390/char/hmcdrv_dev.c
+++ b/drivers/s390/char/hmcdrv_dev.c
@@ -244,24 +244,17 @@ static ssize_t hmcdrv_dev_write(struct file *fp, const char __user *ubuf,
size_t len, loff_t *pos)
{
ssize_t retlen;
+ void *pdata;
pr_debug("writing file '/dev/%pD' at pos. %lld with length %zd\n",
fp, (long long) *pos, len);
if (!fp->private_data) { /* first expect a cmd write */
- fp->private_data = kmalloc(len + 1, GFP_KERNEL);
-
- if (!fp->private_data)
- return -ENOMEM;
-
- if (!copy_from_user(fp->private_data, ubuf, len)) {
- ((char *)fp->private_data)[len] = '\0';
- return len;
- }
-
- kfree(fp->private_data);
- fp->private_data = NULL;
- return -EFAULT;
+ pdata = memdup_user_nul(ubuf, len);
+ if (IS_ERR(pdata))
+ return PTR_ERR(pdata);
+ fp->private_data = pdata;
+ return len;
}
retlen = hmcdrv_dev_transfer((char *) fp->private_data,
--
2.51.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] s390/hmcdrv: Replace kmalloc() + copy_from_user() with memdup_user_nul()
2025-09-05 11:02 [PATCH] s390/hmcdrv: Replace kmalloc() + copy_from_user() with memdup_user_nul() Thorsten Blum
@ 2025-09-08 11:50 ` Alexander Gordeev
0 siblings, 0 replies; 2+ messages in thread
From: Alexander Gordeev @ 2025-09-08 11:50 UTC (permalink / raw)
To: Thorsten Blum
Cc: Heiko Carstens, Vasily Gorbik, Christian Borntraeger,
Sven Schnelle, Jan Kara, Christian Brauner, Jeff Layton,
linux-s390, linux-kernel
On Fri, Sep 05, 2025 at 01:02:23PM +0200, Thorsten Blum wrote:
> Replace kmalloc() followed by copy_from_user() with memdup_user_nul() to
> improve and simplify hmcdrv_dev_write(). Remove the manual
> NUL-termination.
>
> No functional changes intended.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
> ---
> drivers/s390/char/hmcdrv_dev.c | 19 ++++++-------------
> 1 file changed, 6 insertions(+), 13 deletions(-)
Applied, thanks!
^ permalink raw reply [flat|nested] 2+ messages in thread
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2025-09-05 11:02 [PATCH] s390/hmcdrv: Replace kmalloc() + copy_from_user() with memdup_user_nul() Thorsten Blum
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