Commit 655e5b7c authored Aug 26, 2014 by Ben Hutchings Committed by Greg Kroah-Hartman Sep 23, 2014

drivers/base: Fix length checks in create_syslog_header()/dev_vprintk_emit()



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 if this happens, so we can
fix the driver or increase the buffer size.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 833c9545

drivers/base/core.c

+9 −0

Original line number	Original line	Diff line number	Diff line
	@@ -2007,6 +2007,8 @@ create_syslog_header(const struct device dev, char hdr, size_t hdrlen)
	return 0;		return 0;

	pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);		pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);
			if (pos >= hdrlen)
			goto overflow;

	/*		/*
	* Add device identifier DEVICE=:		* Add device identifier DEVICE=:
	@@ -2038,7 +2040,14 @@ create_syslog_header(const struct device dev, char hdr, size_t hdrlen)
	"DEVICE=+%s:%s", subsys, dev_name(dev));		"DEVICE=+%s:%s", subsys, dev_name(dev));
	}		}

			if (pos >= hdrlen)
			goto overflow;

	return pos;		return pos;

			overflow:
			dev_WARN(dev, "device/subsystem name too long");
			return 0;
	}		}

	int dev_vprintk_emit(int level, const struct device *dev,		int dev_vprintk_emit(int level, const struct device *dev,