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liblog: Harden log_id check.

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Logd currently checks against LOG_ID_MAX and LOG_ID_KERNEL to
determine if a given log_id is available.  liblog uses only
LOG_ID_KERNEL.  While this matches with the comments in log/log_id.h
to always keep LOG_ID_KERNEL at the end it does not match with other
checks that logd makes, causing inconsistent behavior.  This
inconsistency is noticable on devices that errantly rewrite
LOG_ID_MAX to not equal LOG_ID_KERNEL + 1.  For log buffers with
id's greater than LOG_ID_KERNEL, liblog reports that logd is
unavailable while logd would accept the request.

The guideline is to not use buffer ids above LOG_ID_KERNEL.
This hardening change prevents an inconsistency that results if these
guidelines are not followed.  Partners are urged instead to increase
LOG_ID_KERNEL locally to match their LOG_ID_MAX - 1 when they add new
local log buffers in their private builds.

Signed-off-by: Evan Ralston <eralston@amazon.com>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Test: compiles. no functional change
Change-Id: Icd4b12ac79c1e5cd1d8a32f67a9795797580aad5
This commit is contained in:
Mark Salyzyn 2017-02-14 13:06:12 -08:00
parent 01815fdcc5
commit d69e801fe8
2 changed files with 2 additions and 2 deletions
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2
liblog/logd_reader.c
View file

@ -91,7 +91,7 @@ LIBLOG_HIDDEN struct android_log_transport_read logdLoggerRead = {
static int logdAvailable(log_id_t logId)
{
if (logId > LOG_ID_KERNEL) {
if (logId >= LOG_ID_MAX) {
return -EINVAL;
}
if (logId == LOG_ID_SECURITY) {

2
liblog/logd_writer.c
View file

@ -117,7 +117,7 @@ static void logdClose()
static int logdAvailable(log_id_t logId)
{
if (logId > LOG_ID_SECURITY) {
if (logId >= LOG_ID_MAX || logId == LOG_ID_KERNEL) {
return -EINVAL;
}
if (atomic_load(&logdLoggerWrite.context.sock) < 0) {