netdevsim: prevent bad user input in nsim_dev_health_break_write()

If either a zero count or a large one is provided, kernel can crash.

Fixes: 82c93a87bf8b ("netdevsim: implement couple of testing devlink health reporters")
Reported-by: syzbot+ea40e4294e58b0292f74@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/675c6862.050a0220.37aaf.00b1.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Link: https://patch.msgid.link/20241213172518.2415666-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/netdevsim/health.c b/drivers/net/netdevsim/health.c
index 70e8bdf34be900f744e821fb237641a27bb71a7b..688f05316b5e109fc84222476023f3f1f078cf28 100644 (file)
--- a/drivers/net/netdevsim/health.c
+++ b/drivers/net/netdevsim/health.c
@@ -149,6 +149,8 @@ static ssize_t nsim_dev_health_break_write(struct file *file,
        char *break_msg;
        int err;
 
+       if (count == 0 || count > PAGE_SIZE)
+               return -EINVAL;
        break_msg = memdup_user_nul(data, count);
        if (IS_ERR(break_msg))
                return PTR_ERR(break_msg);