| Message ID | 20210707091045.460-1-jgross@suse.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | e679004dec37566f658a255157d3aed9d762a2b7 |
| Headers | show |
| Series | [v2] xen/hvc: replace BUG_ON() with negative return value | expand |
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,
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)];
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(-)