On Fri, 2013-12-27 at 10:47 -0800, Greg Kroah-Hartman wrote: > On Fri, Dec 27, 2013 at 06:18:18PM +0100, Ben Hutchings wrote: > > snprintf() returns the number of bytes that could have been written > > (excluding the null), not the actual number of bytes written. Given a > > long enough subsystem or device name, these functions will advance > > beyond the end of the on-stack buffer in dev_vprintk_exit(), resulting > > in an information leak or stack corruption. I don't know whether such > > a long name is currently possible. > > > > In case snprintf() returns a value >= the buffer size, do not add > > structured logging information. Also WARN the first time this > > happens, so we can fix the driver or increase the buffer size. > > > > Signed-off-by: Ben Hutchings <b...@decadent.org.uk> > > --- > > drivers/base/core.c | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/drivers/base/core.c b/drivers/base/core.c > > index 67b180d..989a93c 100644 > > --- a/drivers/base/core.c > > +++ b/drivers/base/core.c > > @@ -2022,6 +2022,8 @@ create_syslog_header(const struct device *dev, char > > *hdr, size_t hdrlen) > > return 0; > > > > pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys); > > + if (pos >= hdrlen) > > + goto overflow; > > > > /* > > * Add device identifier DEVICE=: > > @@ -2053,7 +2055,14 @@ create_syslog_header(const struct device *dev, char > > *hdr, size_t hdrlen) > > "DEVICE=+%s:%s", subsys, dev_name(dev)); > > } > > > > + if (pos >= hdrlen) > > + goto overflow; > > + > > return pos; > > + > > +overflow: > > + dev_WARN_ONCE(dev, 1, "device/subsystem name too long"); > > Why only warn once? Any device/subsystem mix should be complained > about, if for only that we should be really annoying about it to get it > resolved.
This would expand the volume of logging for the problem device by a factor of ~50 so it doesn't seem like a good failure mode. Ben. -- Ben Hutchings Computers are not intelligent. They only think they are.
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