Messages in this thread Patch in this message | | | From | Colin King <> | Subject | [PATCH][V2] n_tty: check for negative and zero space return from tty_write_room | Date | Sat, 30 Mar 2019 00:46:28 +0000 |
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From: Colin Ian King <colin.king@canonical.com>
The return from tty_write_room could potentially be negative if a tty write_room driver returns an error number (not that any seem to do). Rather than just check for a zero return, also check for a -ve return. This avoids the unsigned nr being set to a large unsigned value on the assignment from variable space and can lead to overflowing the buffer buf. Better to be safe than assume all write_room implementations in tty drivers are going to do the right thing.
Signed-off-by: Colin Ian King <colin.king@canonical.com> ---
V2: return the error code from tty_write_room rather than zero, thanks to Dan Carpenter for suggesting this improvement.
--- drivers/tty/n_tty.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index 9cdb0fa3c4bf..f9c584244f72 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -550,9 +550,9 @@ static ssize_t process_output_block(struct tty_struct *tty, mutex_lock(&ldata->output_lock); space = tty_write_room(tty); - if (!space) { + if (space <= 0) { mutex_unlock(&ldata->output_lock); - return 0; + return space; } if (nr > space) nr = space; -- 2.20.1
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