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liblog: do better checks of log messages.

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Testing:

The following test cases all passed and generated log entries:

 # echo -n '\03foo\0bar\0' > /dev/log/main
 # echo -n '\03\0bar\0' > /dev/log/main
 # echo -n '\03\0a\0' > /dev/log/main

The following entries were successfully processed by
logcat but produced no log entries:

 # echo -n '\03\0\0' > /dev/log/main
 # echo -n '\03a\0\0' > /dev/log/main
 # echo -n '\03b\0\0' > /dev/log/main

Also tested the pathological error condition:

 cat /dev/urandom > /dev/log/main

which produced many "+++ LOG: malformed log entry" errors.

Bug: 5478600
Change-Id: I53bc79507242dcfc14445746c29edf47be0a90b4
This commit is contained in:
Nick Kralevich 2011-10-18 15:23:33 -07:00
parent 4423df76f5
commit e1ede1530f
1 changed files with 19 additions and 14 deletions
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33
liblog/logprint.c
View file

@ -352,7 +352,6 @@ int android_log_processLogBuffer(struct logger_entry *buf,
{
entry->tv_sec = buf->sec;
entry->tv_nsec = buf->nsec;
entry->priority = buf->msg[0];
entry->pid = buf->pid;
entry->tid = buf->tid;
@ -360,26 +359,32 @@ int android_log_processLogBuffer(struct logger_entry *buf,
* format: <priority:1><tag:N>\0<message:N>\0
*
* tag str
* starts at msg+1
* starts at buf->msg+1
* msg
* starts at msg+1+len(tag)+1
* starts at buf->msg+1+len(tag)+1
*/
entry->tag = buf->msg + 1;
const size_t tag_len = strlen(entry->tag);
const size_t preambleAndNullLen = tag_len + 3;
if (buf->len <= preambleAndNullLen) {
fprintf(stderr, "+++ LOG: entry corrupt or truncated\n");
if (buf->len < 3) {
// An well-formed entry must consist of at least a priority
// and two null characters
fprintf(stderr, "+++ LOG: entry too small\n");
return -1;
}
entry->messageLen = buf->len - preambleAndNullLen;
entry->message = entry->tag + tag_len + 1;
if (entry->messageLen != strlen(entry->message)) {
fprintf(stderr,
"+++ LOG: Message length inconsistent. Expected %d, got %d\n",
entry->messageLen, strlen(entry->message));
int nullsFound = 0;
int i;
for (i = 1; i < buf->len; i++) {
if (buf->msg[i] == '\0') {
nullsFound++;
}
}
if (nullsFound != 2) {
fprintf(stderr, "+++ LOG: malformed log entry\n");
return -1;
}
entry->priority = buf->msg[0];
entry->tag = buf->msg + 1;
entry->message = entry->tag + strlen(entry->tag) + 1;
entry->messageLen = strlen(entry->message);
return 0;
}