On Tue, Mar 19, 2019 at 1:35 PM Sergey Senozhatsky
<sergey.senozhat...@gmail.com> wrote:
>
> On (03/19/19 09:10), Dmitry Vyukov wrote:
>
> [..]
>
> > In some setups we read out output with "dmesg -w" (should stream
> > output as well) in absence of a better solution. Will this be affected
> > by SYSLOG_ACTION_CLEAR?
>
> There is a small chance that syslog/devkmsg can be affected
>
> syslog_clear()
> {
> clear_seq = log_next_seq;
> clear_idx = log_next_idx;
> }
>
> syslog_print_all()
> {
> ...
> seq = clear_seq;
> idx = clear_idx;
> while (seq < log_next_seq) {
> ...
> len += msg_print_text(msg, true, time, NULL, 0);
> }
> ...
> }
>
> devkmsg also may be affected
>
> syslog_clear()
> {
> clear_seq = log_next_seq;
> clear_idx = log_next_idx;
> }
>
> devkmsg_llseek()
> {
> ...
> case SEEK_DATA:
> user->idx = clear_idx;
> user->seq = clear_seq;
> break;
> ...
> }
>
> user->idx/user->seq then are used in devkmsg poll()/read(). syslog is
> more likely to be affected, I think.
SYSLOG_ACTION_CLEAR is disabled:
https://github.com/google/syzkaller/commit/28c04d39e052ee2960eebc16a3f7fba88920cd52
