printk: Fix possible console use-after-free

When emitting a record via legacy printing, it is possible that a handover
to another legacy printing context occurs. When a context has performed a
handover, the console SRCU read lock is released and the pointer to the
console struct might now be invalid. Therefore, after calling
nbcon_legacy_emit_next_record() or console_emit_next_record(), it is
necessary to check if a handover occurred _before_ further @con usage.

Sashiko pointed out that console_flush_one_record() was not doing this.

In console_flush_one_record(), after emitting a record, move the further
usage of @con after the handover check.

Fixes: c158834b223f ("printk: nbcon: Use nbcon consoles in console_flush_all()")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/lkml/20260630170903.099D61F000E9@smtp.kernel.org
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://patch.msgid.link/20260703141521.202813-1-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>

0 files changed, 0 insertions, 0 deletions