drivers/tty/hvc/hvc_xen.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
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 <jgross@suse.com>
---
V2:
- drop BUG_ON() (Christophe Leroy, Greg Kroah-Hartmann)
- replace WARN_ONCE() by pr_err_once() (Greg Kroah-Hartmann)
- break out from original series
---
drivers/tty/hvc/hvc_xen.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 92c9a476defc..8f143c09a169 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -86,7 +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 */
- BUG_ON((prod - cons) > sizeof(intf->out));
+
+ if ((prod - cons) > sizeof(intf->out)) {
+ pr_err_once("xencons: Illegal ring page indices");
+ return -EINVAL;
+ }
while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
@@ -114,7 +118,10 @@ 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 +145,11 @@ 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 ((prod - cons) > sizeof(intf->in)) {
+ pr_err_once("xencons: Illegal ring page indices");
+ return -EINVAL;
+ }
while (cons != prod && recv < len)
buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
--
2.26.2
On 07.07.2021 11:10, 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 <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> > --- a/drivers/tty/hvc/hvc_xen.c > +++ b/drivers/tty/hvc/hvc_xen.c > @@ -86,7 +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 */ Largely unrelated note: While in general the barriers here may want switching to virt_*mb(), this particular one looks to be too heavy anyway: a read barrier is all that's needed here afaict, just like there's only a write barrier between ring contents and producer writing in __write_console(). And btw, since I've got puzzled by the linuxppc-dev@ in the recipients list, I did look up relevant entries in ./MAINTAINERS. Shouldn't the file be part of "XEN HYPERVISOR INTERFACE"? Jan
On 07.07.21 11:57, Jan Beulich wrote: > On 07.07.2021 11:10, 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 <jgross@suse.com> > > Reviewed-by: Jan Beulich <jbeulich@suse.com> > >> --- a/drivers/tty/hvc/hvc_xen.c >> +++ b/drivers/tty/hvc/hvc_xen.c >> @@ -86,7 +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 */ > > Largely unrelated note: While in general the barriers here may want > switching to virt_*mb(), this particular one looks to be too heavy > anyway: a read barrier is all that's needed here afaict, just like > there's only a write barrier between ring contents and producer > writing in __write_console(). I agree. > And btw, since I've got puzzled by the linuxppc-dev@ in the recipients > list, I did look up relevant entries in ./MAINTAINERS. Shouldn't the > file be part of "XEN HYPERVISOR INTERFACE"? I wouldn't mind. Greg, Jiri, what do you think? Juergen
On 07. 07. 21, 12:40, Juergen Gross wrote: >> And btw, since I've got puzzled by the linuxppc-dev@ in the recipients >> list, I did look up relevant entries in ./MAINTAINERS. Shouldn't the >> file be part of "XEN HYPERVISOR INTERFACE"? > > I wouldn't mind. Greg, Jiri, what do you think? /me concurs. thanks, -- js suse labs
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