Greg, Jiri, will you pick up these patches? On 2018/05/26 1:12, Greg KH wrote: > On Thu, May 17, 2018 at 07:11:01AM -0700, syzbot wrote: >> Hello, >> >> syzbot has tested the proposed patch and the reproducer did not trigger >> crash: > > Great! Is the patch going to be submitted "properly" so that I can > queue it up? :) > > thanks, > > greg k-h >
On 2018/05/26 9:53, Tetsuo Handa wrote: > syzbot is reporting stalls at n_tty_receive_char_special() [1]. This is > because comparison is not working as expected since ldata->read_head can > change at any moment. Mitigate this by explicitly masking with buffer size > when checking condition for "while" loops. > > [1] > https://syzkaller.appspot.com/bug?id=3d7481a346958d9469bebbeb0537d5f056bdd6e8 > > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > Reported-by: syzbot <syzbot+18df353d7540aa6b5...@syzkaller.appspotmail.com> > Fixes: bc5a5e3f45d04784 ("n_tty: Don't wrap input buffer indices at buffer > size") > Cc: Peter Hurley <pe...@hurleysoftware.com> > --- > drivers/tty/n_tty.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > On 2018/05/26 9:53, Tetsuo Handa wrote: > syzbot is reporting stalls at __process_echoes() [1]. This is because > since ldata->echo_commit < ldata->echo_tail becomes true for some reason, > the discard loop is serving as almost infinite loop. This patch tries to > avoid falling into ldata->echo_commit < ldata->echo_tail situation by > making access to echo_* variables more carefully. > > Since reset_buffer_flags() is called without output_lock held, it should > not touch echo_* variables. And omit a call to reset_buffer_flags() from > n_tty_open() by using vzalloc(). > > Since add_echo_byte() is called without output_lock held, it needs memory > barrier between storing into echo_buf[] and incrementing echo_head counter. > echo_buf() needs corresponding memory barrier before reading echo_buf[]. > Lack of handling the possibility of not-yet-stored multi-byte operation > might be the reason of falling into ldata->echo_commit < ldata->echo_tail > situation, for if I do WARN_ON(ldata->echo_commit == tail + 1) prior to > echo_buf(ldata, tail + 1), the WARN_ON() fires. > > Also, explicitly masking with buffer for the former "while" loop, and > use ldata->echo_commit > tail for the latter "while" loop. > > [1] > https://syzkaller.appspot.com/bug?id=17f23b094cd80df750e5b0f8982c521ee6bcbf40 > > Signed-off-by: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> > Reported-by: syzbot <syzbot+108696293d7a21ab6...@syzkaller.appspotmail.com> > Cc: Peter Hurley <pe...@hurleysoftware.com> > --- > drivers/tty/n_tty.c | 42 ++++++++++++++++++++++++------------------ > 1 file changed, 24 insertions(+), 18 deletions(-)
