[Linux-kernel-mentees] [PATCH] net: rose: Fix Null pointer dereference in rose_send_frame()
gregkh at linuxfoundation.org
Thu Oct 15 05:12:25 UTC 2020
On Thu, Oct 15, 2020 at 05:47:12AM +0530, Anmol Karn wrote:
> In rose_send_frame(), when comparing two ax.25 addresses, it assigns rose_call to
> either global ROSE callsign or default port, but when the former block triggers and
> rose_call is assigned by (ax25_address *)neigh->dev->dev_addr, a NULL pointer is
> dereferenced by 'neigh' when dereferencing 'dev'.
> - net/rose/rose_link.c
> This bug seems to get triggered in this line:
> rose_call = (ax25_address *)neigh->dev->dev_addr;
> Prevent it by checking NULL condition for neigh->dev before comparing addressed for
> rose_call initialization.
> Reported-by: syzbot+a1c743815982d9496393 at syzkaller.appspotmail.com
> Link: https://syzkaller.appspot.com/bug?id=9d2a7ca8c7f2e4b682c97578dfa3f236258300b3
> Signed-off-by: Anmol Karn <anmol.karan123 at gmail.com>
> I am bit sceptical about the error return code, please suggest if anything else is
> appropriate in place of '-ENODEV'.
> net/rose/rose_link.c | 3 +++
> 1 file changed, 3 insertions(+)
> diff --git a/net/rose/rose_link.c b/net/rose/rose_link.c
> index f6102e6f5161..92ea6a31d575 100644
> --- a/net/rose/rose_link.c
> +++ b/net/rose/rose_link.c
> @@ -97,6 +97,9 @@ static int rose_send_frame(struct sk_buff *skb, struct rose_neigh *neigh)
> ax25_address *rose_call;
> ax25_cb *ax25s;
> + if (!neigh->dev)
> + return -ENODEV;
How can ->dev not be set at this point in time? Shouldn't that be
fixed, because it could change right after you check this, right?
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