[PATCH -next V2] sysctl: returns -EINVAL when a negative value is passed to proc_doulongvec_minmax

When we pass a negative value to the proc_doulongvec_minmax() function,
the function returns 0, but the corresponding interface value does not
change.

we can easily reproduce this problem with the following commands:
    `cd /proc/sys/fs/epoll`
    `echo -1 > max_user_watches; echo $?; cat max_user_watches`

This function requires a non-negative number to be passed in, so when
a negative number is passed in, -EINVAL is returned.

Reported-by: Hulk Robot <redacted>
Signed-off-by: Baokun Li <redacted>
---
V1->V2:
	Modify the judgment position.

 kernel/sysctl.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7f07b058b180..4211e39a5fd3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c

@@ -1147,10 +1147,11 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table,
 			err = proc_get_long(&p, &left, &val, &neg,
 					     proc_wspace_sep,
 					     sizeof(proc_wspace_sep), NULL);
-			if (err)
+			if (err || neg) {
+				err = -EINVAL;
 				break;
-			if (neg)
-				continue;
+			}
+
 			val = convmul * val / convdiv;
 			if ((min && val < *min) || (max && val > *max)) {
 				err = -EINVAL;

-- 
2.31.1

On Mon, Dec 20, 2021 at 05:26:27PM +0800, Baokun Li wrote:

When we pass a negative value to the proc_doulongvec_minmax() function,
the function returns 0, but the corresponding interface value does not
change.

we can easily reproduce this problem with the following commands:
    `cd /proc/sys/fs/epoll`
    `echo -1 > max_user_watches; echo $?; cat max_user_watches`

This function requires a non-negative number to be passed in, so when
a negative number is passed in, -EINVAL is returned.

Reported-by: Hulk Robot <redacted>
Signed-off-by: Baokun Li <redacted>

Acked-by: Luis Chamberlain <mcgrof@kernel.org>

 Luis

在 2021/12/21 3:17, Luis Chamberlain 写道:

On Mon, Dec 20, 2021 at 05:26:27PM +0800, Baokun Li wrote:

quoted

When we pass a negative value to the proc_doulongvec_minmax() function,
the function returns 0, but the corresponding interface value does not
change.

we can easily reproduce this problem with the following commands:
     `cd /proc/sys/fs/epoll`
     `echo -1 > max_user_watches; echo $?; cat max_user_watches`

This function requires a non-negative number to be passed in, so when
a negative number is passed in, -EINVAL is returned.

Reported-by: Hulk Robot <redacted>
Signed-off-by: Baokun Li <redacted>

Acked-by: Luis Chamberlain <mcgrof@kernel.org>

  Luis
.

Thank you for your Ack.

-- 
With Best Regards,
Baokun Li