* [PATCH] n_tty: check for negative and zero space return from tty_write_room
@ 2019-03-28 17:10 Colin King
2019-03-28 19:34 ` Mukesh Ojha
2019-03-29 7:43 ` Dan Carpenter
0 siblings, 2 replies; 3+ messages in thread
From: Colin King @ 2019-03-28 17:10 UTC (permalink / raw)
To: Greg Kroah-Hartman, Jiri Slaby; +Cc: kernel-janitors, linux-kernel
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>
---
drivers/tty/n_tty.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 9cdb0fa3c4bf..66630787fbf9 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -550,7 +550,7 @@ 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;
}
--
2.20.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] n_tty: check for negative and zero space return from tty_write_room
2019-03-28 17:10 [PATCH] n_tty: check for negative and zero space return from tty_write_room Colin King
@ 2019-03-28 19:34 ` Mukesh Ojha
2019-03-29 7:43 ` Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: Mukesh Ojha @ 2019-03-28 19:34 UTC (permalink / raw)
To: Colin King, Greg Kroah-Hartman, Jiri Slaby; +Cc: kernel-janitors, linux-kernel
On 3/28/2019 10:40 PM, Colin King wrote:
> 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>
Looks reasonable to me.
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
-Mukesh.
> ---
> drivers/tty/n_tty.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 9cdb0fa3c4bf..66630787fbf9 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -550,7 +550,7 @@ 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;
> }
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] n_tty: check for negative and zero space return from tty_write_room
2019-03-28 17:10 [PATCH] n_tty: check for negative and zero space return from tty_write_room Colin King
2019-03-28 19:34 ` Mukesh Ojha
@ 2019-03-29 7:43 ` Dan Carpenter
1 sibling, 0 replies; 3+ messages in thread
From: Dan Carpenter @ 2019-03-29 7:43 UTC (permalink / raw)
To: Colin King; +Cc: Greg Kroah-Hartman, Jiri Slaby, kernel-janitors, linux-kernel
On Thu, Mar 28, 2019 at 05:10:05PM +0000, Colin King wrote:
> 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>
> ---
> drivers/tty/n_tty.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 9cdb0fa3c4bf..66630787fbf9 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -550,7 +550,7 @@ 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;
Instead of zero we should probably return "space" to preserve the error
code.
regards,
dan carpenter
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-03-29 7:44 UTC | newest]
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2019-03-28 19:34 ` Mukesh Ojha
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