Messages in this thread | | | Date | Wed, 15 Feb 2023 12:37:36 +0100 | From | Vincent Whitchurch <> | Subject | Re: [PATCH v2] tty: ttynull: implement console write |
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+ Cc: John, Petr
On Tue, Feb 14, 2023 at 12:59:21PM +0100, Michael Thalmeier wrote: > Since commit a699449bb13b ("printk: refactor and rework printing logic"), > con->write is called without checking if it is implemented in the console > driver. This does make some sense, because for all "normal" consoles it > is vital to have a write function. > As the ttynull console driver does not need any console output the write > function was not implemented. This caused a "unable to handle kernel NULL > pointer dereference" when the write function is called now. > > To fix this issue, implement an empty write function. > > Fixes: a699449bb13b ("printk: refactor and rework printing logic") > Cc: stable@vger.kernel.org > Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at>
Looking at the referenced commit, the only place I see it calling con->write() is from call_console_driver(), which is in turn only called from console_emit_next_record(). And console_flush_all(), the only caller of console_emit_next_record(), checks that con->write is not NULL using console_is_usable() before calling console_emit_next_record().
What am I missing? Which code path in the referenced commit calls con->write without checking for NULL?
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