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Commit 84c99136 authored by Luis Hector Chavez's avatar Luis Hector Chavez
Browse files

libcutils: Stop checking the uid of netlink messages 

This is a partial revert of
https://android-review.googlesource.com/c/platform/system/core/+/528619.
The uid-check was done before
https://patchwork.kernel.org/patch/1525551/ was available, and thus is
now unnecessary to perform such check, since we can just rely on the
kernel patch now.

Bug: 71632076
Test: aosp_sailfish-userdebug still works

Change-Id: I1d1319b774483d1714ecb4dd838a20e055acc2a3
parent 830fd168

libcutils/uevent.cpp

+0 −53
Original line number Diff line number Diff line
@@ -27,54 +27,6 @@ 


#include <linux/netlink.h>



#include <fstream>



#include <private/android_filesystem_config.h>



namespace {



// Returns the uid of root in the current user namespace.

// Returns AID_OVERFLOWUID if the root user is not mapped in the current

// namespace.

// Returns 0 if the kernel is not user namespace-aware (for backwards

// compatibility) or if AID_OVERFLOWUID could not be validated to match what the

// kernel would return.

uid_t GetRootUid() {

    constexpr uid_t kParentRootUid = 0;



    std::ifstream uid_map_file("/proc/self/uid_map");

    if (!uid_map_file) {

        // The kernel does not support user namespaces.

        return kParentRootUid;

    }



    uid_t current_namespace_uid, parent_namespace_uid;

    uint32_t length;

    while (uid_map_file >> current_namespace_uid >> parent_namespace_uid >> length) {

        // Since kParentRootUid is 0, it should be the first entry in the mapped

        // range.

        if (parent_namespace_uid != kParentRootUid || length < 1) continue;

        return current_namespace_uid;

    }



    // Sanity check: verify that the overflow UID is the one to be returned by

    // the kernel.

    std::ifstream overflowuid_file("/proc/sys/kernel/overflowuid");

    if (!overflowuid_file) {

        // It's better to return 0 in case we cannot make sure that the overflow

        // UID matches.

        return kParentRootUid;

    }

    uid_t kernel_overflow_uid;

    if (!(overflowuid_file >> kernel_overflow_uid) || kernel_overflow_uid != AID_OVERFLOWUID)

        return kParentRootUid;



    // root is unmapped, use the kernel "overflow" uid.

    return AID_OVERFLOWUID;

}



}  // namespace



extern "C" {



/**
@@ -99,7 +51,6 @@ ssize_t uevent_kernel_multicast_uid_recv(int socket, void* buffer, size_t length 
}



ssize_t uevent_kernel_recv(int socket, void* buffer, size_t length, bool require_group, uid_t* uid) {

    static const uid_t root_uid = GetRootUid();

    struct iovec iov = {buffer, length};

    struct sockaddr_nl addr;

    char control[CMSG_SPACE(sizeof(struct ucred))];
@@ -122,10 +73,6 @@ ssize_t uevent_kernel_recv(int socket, void* buffer, size_t length, bool require 


    cred = (struct ucred*)CMSG_DATA(cmsg);

    *uid = cred->uid;

    if (cred->uid != root_uid) {

        /* ignoring netlink message from non-root user */

        goto out;

    }



    if (addr.nl_pid != 0) {

        /* ignore non-kernel */