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 <b...@decadent.org.uk>
---
v2: use dev_WARN() not dev_WARN_ON()
drivers/base/core.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 20da3ad..062b7bf 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -2007,6 +2007,8 @@ 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=:
@@ -2038,7 +2040,14 @@ 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(dev, 1, "device/subsystem name too long");
+ return 0;
}
int dev_vprintk_emit(int level, const struct device *dev,
--
Ben Hutchings
Never attribute to conspiracy what can adequately be explained by stupidity.
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