On 13.05.21 12:25, Greg Kroah-Hartman wrote:
On Thu, May 13, 2021 at 12:03:02PM +0200, Juergen Gross wrote:Xen frontends shouldn't BUG() in case of illegal data received from their backends. So replace the BUG_ON()s when reading illegal data from the ring page with negative return values.Signed-off-by: Juergen Gross <jgr...@suse.com> --- drivers/tty/hvc/hvc_xen.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c index 92c9a476defc..30d7ffb1e04c 100644 --- a/drivers/tty/hvc/hvc_xen.c +++ b/drivers/tty/hvc/hvc_xen.c @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons, cons = intf->out_cons; prod = intf->out_prod; mb(); /* update queue values before going on */ + + if (WARN_ONCE((prod - cons) > sizeof(intf->out), + "Illegal ring page indices")) + return -EINVAL;How nice, you just rebooted on panic-on-warn systems :(+ BUG_ON((prod - cons) > sizeof(intf->out));Why keep this line?
Failed to delete it, sorry.
Please just fix this up properly, if userspace can trigger this, then both the WARN_ON() and BUG_ON() are not correct and need to be correctly handled.
It can be triggered by the console backend, but I agree a WARN isn't the way to go here. Juergen
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