Daniel Kurtz c91d00e0f3 os/log: refactor logging ...

It is not safe to ever use an arbitrary (possibly user supplied) string as
part of the format for a *sprintf() call.

For example:
  1. Name a Bluetooth keyboard "%n%n%n%n%n%n%n%n"
  2. Pair it with a computer running X and try to use it
  3. X is not happy when trying to do the following in xf86-input-evdev:
     xf86IDrvMsg(pInfo, X_CONFIG, "Device: \"%s\"\n", device);
     because LogVHdrMessageVerb() has put the %n from the device name
     into a format string of the form:
        "evdev: %n%n%n%n%n%n%n%n: Device: \"%s\"\n"

Instead, build up a log message in place by appending successive formatted
strings by sncprintf'ing to the end of the previous.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

2012-05-03 14:59:23 +10:00

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