Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
On 13.05.21 12:25, Greg Kroah-Hartman wrote: On Thu, May 13, 2021 at 12:03:02PM +0200, Juergen Gross wrote: Xen frontends shouldn't BUG() in case of illegal data received from their backends. So replace the BUG_ON()s when reading illegal data from the ring page with negative return values. Signed-off-by: Juergen Gross --- drivers/tty/hvc/hvc_xen.c | 15 +-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c index 92c9a476defc..30d7ffb1e04c 100644 --- a/drivers/tty/hvc/hvc_xen.c +++ b/drivers/tty/hvc/hvc_xen.c @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons, cons = intf->out_cons; prod = intf->out_prod; mb(); /* update queue values before going on */ + + if (WARN_ONCE((prod - cons) > sizeof(intf->out), + "Illegal ring page indices")) + return -EINVAL; How nice, you just rebooted on panic-on-warn systems :( + BUG_ON((prod - cons) > sizeof(intf->out)); Why keep this line? Failed to delete it, sorry. Please just fix this up properly, if userspace can trigger this, then both the WARN_ON() and BUG_ON() are not correct and need to be correctly handled. It can be triggered by the console backend, but I agree a WARN isn't the way to go here. Juergen OpenPGP_0xB0DE9DD628BF132F.asc Description: application/pgp-keys OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
On Thu, May 13, 2021 at 12:03:02PM +0200, Juergen Gross wrote:
> Xen frontends shouldn't BUG() in case of illegal data received from
> their backends. So replace the BUG_ON()s when reading illegal data from
> the ring page with negative return values.
>
> Signed-off-by: Juergen Gross
> ---
> drivers/tty/hvc/hvc_xen.c | 15 +--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
> index 92c9a476defc..30d7ffb1e04c 100644
> --- a/drivers/tty/hvc/hvc_xen.c
> +++ b/drivers/tty/hvc/hvc_xen.c
> @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons,
> cons = intf->out_cons;
> prod = intf->out_prod;
> mb(); /* update queue values before going on */
> +
> + if (WARN_ONCE((prod - cons) > sizeof(intf->out),
> + "Illegal ring page indices"))
> + return -EINVAL;
How nice, you just rebooted on panic-on-warn systems :(
> +
> BUG_ON((prod - cons) > sizeof(intf->out));
Why keep this line?
Please just fix this up properly, if userspace can trigger this, then
both the WARN_ON() and BUG_ON() are not correct and need to be correctly
handled.
>
> while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
> @@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const
> char *data, int len)
>*/
> while (len) {
> int sent = __write_console(cons, data, len);
> -
> +
> + if (sent < 0)
> + return sent;
> +
> data += sent;
> len -= sent;
>
> @@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char
> *buf, int len)
> cons = intf->in_cons;
> prod = intf->in_prod;
> mb(); /* get pointers before reading ring */
> - BUG_ON((prod - cons) > sizeof(intf->in));
> +
> + if (WARN_ONCE((prod - cons) > sizeof(intf->in),
> + "Illegal ring page indices"))
> + return -EINVAL;
Same here, you still just paniced a machine :(
thanks,
greg k-h
Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
On 13.05.21 12:16, Christophe Leroy wrote: Le 13/05/2021 à 12:03, Juergen Gross a écrit : Xen frontends shouldn't BUG() in case of illegal data received from their backends. So replace the BUG_ON()s when reading illegal data from the ring page with negative return values. Signed-off-by: Juergen Gross --- drivers/tty/hvc/hvc_xen.c | 15 +-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c index 92c9a476defc..30d7ffb1e04c 100644 --- a/drivers/tty/hvc/hvc_xen.c +++ b/drivers/tty/hvc/hvc_xen.c @@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons, cons = intf->out_cons; prod = intf->out_prod; mb(); /* update queue values before going on */ + + if (WARN_ONCE((prod - cons) > sizeof(intf->out), + "Illegal ring page indices")) + return -EINVAL; + BUG_ON((prod - cons) > sizeof(intf->out)); Why keep the BUG_ON() ? Oh, failed to delete it. Thanks for noticing. Juergen OpenPGP_0xB0DE9DD628BF132F.asc Description: application/pgp-keys OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
Le 13/05/2021 à 12:03, Juergen Gross a écrit :
Xen frontends shouldn't BUG() in case of illegal data received from
their backends. So replace the BUG_ON()s when reading illegal data from
the ring page with negative return values.
Signed-off-by: Juergen Gross
---
drivers/tty/hvc/hvc_xen.c | 15 +--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 92c9a476defc..30d7ffb1e04c 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons,
cons = intf->out_cons;
prod = intf->out_prod;
mb(); /* update queue values before going on */
+
+ if (WARN_ONCE((prod - cons) > sizeof(intf->out),
+ "Illegal ring page indices"))
+ return -EINVAL;
+
BUG_ON((prod - cons) > sizeof(intf->out));
Why keep the BUG_ON() ?
while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
@@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const char
*data, int len)
*/
while (len) {
int sent = __write_console(cons, data, len);
-
+
+ if (sent < 0)
+ return sent;
+
data += sent;
len -= sent;
@@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char *buf, int len)
cons = intf->in_cons;
prod = intf->in_prod;
mb(); /* get pointers before reading ring */
- BUG_ON((prod - cons) > sizeof(intf->in));
+
+ if (WARN_ONCE((prod - cons) > sizeof(intf->in),
+ "Illegal ring page indices"))
+ return -EINVAL;
while (cons != prod && recv < len)
buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
[PATCH 8/8] xen/hvc: replace BUG_ON() with negative return value
Xen frontends shouldn't BUG() in case of illegal data received from
their backends. So replace the BUG_ON()s when reading illegal data from
the ring page with negative return values.
Signed-off-by: Juergen Gross
---
drivers/tty/hvc/hvc_xen.c | 15 +--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 92c9a476defc..30d7ffb1e04c 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -86,6 +86,11 @@ static int __write_console(struct xencons_info *xencons,
cons = intf->out_cons;
prod = intf->out_prod;
mb(); /* update queue values before going on */
+
+ if (WARN_ONCE((prod - cons) > sizeof(intf->out),
+ "Illegal ring page indices"))
+ return -EINVAL;
+
BUG_ON((prod - cons) > sizeof(intf->out));
while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
@@ -114,7 +119,10 @@ static int domU_write_console(uint32_t vtermno, const char
*data, int len)
*/
while (len) {
int sent = __write_console(cons, data, len);
-
+
+ if (sent < 0)
+ return sent;
+
data += sent;
len -= sent;
@@ -138,7 +146,10 @@ static int domU_read_console(uint32_t vtermno, char *buf,
int len)
cons = intf->in_cons;
prod = intf->in_prod;
mb(); /* get pointers before reading ring */
- BUG_ON((prod - cons) > sizeof(intf->in));
+
+ if (WARN_ONCE((prod - cons) > sizeof(intf->in),
+ "Illegal ring page indices"))
+ return -EINVAL;
while (cons != prod && recv < len)
buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
--
2.26.2
