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Commit e0b8ccd1 authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

logd: inherit android_get_control_file() 

Setup and then collect from the environment /proc/kmsg and /dev/kmsg
file descriptors. Do not do so for logcat --reinit.

Test: gTest logd-unit-tests, liblog-unit-tests and logcat-unit-tests
Bug: 32450474
Change-Id: Ied537ca561fcd4e71a9ad9c57398a23ba23f6ced
parent 62767fe2

logd/logd.rc

+2 −0
Original line number Diff line number Diff line
@@ -2,6 +2,8 @@ service logd /system/bin/logd 
    socket logd stream 0666 logd logd

    socket logdr seqpacket 0666 logd logd

    socket logdw dgram 0222 logd logd

    file /proc/kmsg r

    file /dev/kmsg w

    group root system readproc

    writepid /dev/cpuset/system-background/tasks

logd/main.cpp

+28 −16
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ 
#include <android-base/macros.h>

#include <cutils/properties.h>

#include <cutils/sched_policy.h>

#include <cutils/files.h>

#include <cutils/sockets.h>

#include <libminijail.h>

#include <log/event_tag_map.h>
@@ -189,11 +190,11 @@ static void *reinit_thread_start(void * /*obj*/) { 
    set_sched_policy(0, SP_BACKGROUND);

    setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND);



    // If we are AID_ROOT, we should drop to AID_SYSTEM, if we are anything

    // else, we have even lesser privileges and accept our fate. Not worth

    // checking for error returns setting this thread's privileges.

    (void)setgid(AID_SYSTEM);

    (void)setuid(AID_SYSTEM);

    // If we are AID_ROOT, we should drop to AID_LOGD+AID_SYSTEM, if we are

    // anything else, we have even lesser privileges and accept our fate. Not

    // worth checking for error returns setting this thread's privileges.

    (void)setgid(AID_SYSTEM); // readonly access to /data/system/packages.list

    (void)setuid(AID_LOGD);   // access to everything logd.



    while (reinit_running && !sem_wait(&reinit) && reinit_running) {
@@ -318,17 +319,6 @@ static void readDmesg(LogAudit *al, LogKlog *kl) { 
// logging plugins like auditd and restart control. Additional

// transitory per-client threads are created for each reader.

int main(int argc, char *argv[]) {

    int fdPmesg = -1;

    bool klogd = __android_logger_property_get_bool("logd.kernel",

                                                    BOOL_DEFAULT_TRUE |

                                                    BOOL_DEFAULT_FLAG_PERSIST |

                                                    BOOL_DEFAULT_FLAG_ENG |

                                                    BOOL_DEFAULT_FLAG_SVELTE);

    if (klogd) {

        fdPmesg = open("/proc/kmsg", O_RDONLY | O_NDELAY);

    }

    fdDmesg = open("/dev/kmsg", O_WRONLY);



    // issue reinit command. KISS argument parsing.

    if ((argc > 1) && argv[1] && !strcmp(argv[1], "--reinit")) {

        int sock = TEMP_FAILURE_RETRY(
@@ -364,6 +354,28 @@ int main(int argc, char *argv[]) { 
        return strncmp(buffer, success, sizeof(success) - 1) != 0;

    }



    static const char dev_kmsg[] = "/dev/kmsg";

    fdDmesg = android_get_control_file(dev_kmsg);

    if (fdDmesg < 0) {

        fdDmesg = TEMP_FAILURE_RETRY(open(dev_kmsg, O_WRONLY | O_CLOEXEC));

    }



    int fdPmesg = -1;

    bool klogd = __android_logger_property_get_bool("logd.kernel",

                                                    BOOL_DEFAULT_TRUE |

                                                    BOOL_DEFAULT_FLAG_PERSIST |

                                                    BOOL_DEFAULT_FLAG_ENG |

                                                    BOOL_DEFAULT_FLAG_SVELTE);

    if (klogd) {

        static const char proc_kmsg[] = "/proc/kmsg";

        fdPmesg = android_get_control_file(proc_kmsg);

        if (fdPmesg < 0) {

            fdPmesg = TEMP_FAILURE_RETRY(open(proc_kmsg,

                                              O_RDONLY | O_NDELAY | O_CLOEXEC));

        }

        if (fdPmesg < 0) android::prdebug("Failed to open %s\n", proc_kmsg);

    }



    // Reinit Thread

    sem_init(&reinit, 0, 0);

    sem_init(&uidName, 0, 0);