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Commit 812d7698 authored by Bart Van Assche's avatar Bart Van Assche
Browse files

Fix the cgroup directory owner in createProcessGroupInternal() 



Without this patch attempts to modify the blkio cgroup attributes by
/system/bin/mediaserver fail as follows:

03-23 09:27:59.542   517  1811 E libprocessgroup: Failed to write '100' to /sys/fs/cgroup/./uid_1013/pid_517/io.bfq.weight: Permission denied

This is because the mediaserver process is started as user 'media',
because the mediaserver process is not in the system group and hence
does not have permission to write into a directory with the following
owner, group and permissions:

vsoc_x86_64:/ # ls -ld /sys/fs/cgroup/./uid_1013/pid_517/io.bfq.weight
-rwxrwxr-x 1 system system 0 2022-03-23 09:27 /sys/fs/cgroup/./uid_1013/pid_517/io.bfq.weight

Bug: 213617178
Test: Booted Android in Cuttlefish and inspected logcat.
Change-Id: I788acc9a137ae29898177f492cae2f954a9c811c
Signed-off-by: default avatarBart Van Assche <bvanassche@google.com>
parent a6c82269

libprocessgroup/processgroup.cpp

+2 −4
Original line number Diff line number Diff line
@@ -460,7 +460,6 @@ static int createProcessGroupInternal(uid_t uid, int initialPid, std::string cgr 


    struct stat cgroup_stat;

    mode_t cgroup_mode = 0750;

    uid_t cgroup_uid = AID_SYSTEM;

    gid_t cgroup_gid = AID_SYSTEM;

    int ret = 0;
@@ -468,11 +467,10 @@ static int createProcessGroupInternal(uid_t uid, int initialPid, std::string cgr 
        PLOG(ERROR) << "Failed to get stats for " << cgroup;

    } else {

        cgroup_mode = cgroup_stat.st_mode;

        cgroup_uid = cgroup_stat.st_uid;

        cgroup_gid = cgroup_stat.st_gid;

    }



    if (!MkdirAndChown(uid_path, cgroup_mode, cgroup_uid, cgroup_gid)) {

    if (!MkdirAndChown(uid_path, cgroup_mode, uid, cgroup_gid)) {

        PLOG(ERROR) << "Failed to make and chown " << uid_path;

        return -errno;

    }
@@ -486,7 +484,7 @@ static int createProcessGroupInternal(uid_t uid, int initialPid, std::string cgr 


    auto uid_pid_path = ConvertUidPidToPath(cgroup.c_str(), uid, initialPid);



    if (!MkdirAndChown(uid_pid_path, cgroup_mode, cgroup_uid, cgroup_gid)) {

    if (!MkdirAndChown(uid_pid_path, cgroup_mode, uid, cgroup_gid)) {

        PLOG(ERROR) << "Failed to make and chown " << uid_pid_path;

        return -errno;

    }