linux-kernel - Re: [PATCH v2] kobject: Fix global-out-of-bounds in kobject_action

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Date:   Thu, 9 Mar 2023 12:01:24 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Xia Fukun <xiafukun@...wei.com>
Cc:     prajnoha@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kobject: Fix global-out-of-bounds in
 kobject_action_type()

On Wed, Mar 08, 2023 at 11:59:30AM +0800, Xia Fukun wrote:
> The following c language code can trigger KASAN's global variable
> out-of-bounds access error in kobject_action_type():
> 
> int main() {
>     int fd;
>     char *filename = "/sys/block/ram12/uevent";
>     char str[86] = "offline";
>     int len = 86;
> 
>     fd = open(filename, O_WRONLY);
>     if (fd == -1) {
>         printf("open");
>         exit(1);
>     }
> 
>     if (write(fd, str, len) == -1) {
>         printf("write");
>         exit(1);
>     }
> 
>     close(fd);
>     return 0;
> }
> 
> Function kobject_action_type() receives the input parameters buf and count,
> where count is the length of the string buf.
> 
> In the use case we provided, count is 86, the count_first is 85.
> Buf points to a string with a length of 86, and its first seven
> characters are "offline".
> In line 87 of the code, kobject_actions[action] is the string "offline"
> with the length of 7,an out-of-boundary access will appear:
> 
> kobject_actions[action][85].
> 
> Modify the judgment logic in line 87. If the length of the string
> kobject_actions[action] is greater than count_first(e.g. buf is "off",
> count is 3), continue the loop.
> Otherwise, the match is considered successful.
> 
> This change means that our test case will be successfully parsed as an
> offline event and no out-of-bounds access error will occur.
> 
> Fixes: f36776fafbaa ("kobject: support passing in variables for synthetic uevents")
> Signed-off-by: Xia Fukun <xiafukun@...wei.com>
> ---
> v1 -> v2:
> - modify the matching logic

I see 2 v2 patches in my queue, with no way to tell which one is
correct.

Please fix up and send a v3.

thanks,

greg k-h