Re: [PATCH net] Bluetooth: hci_event: fix double hci_conn_drop() when conn->state == BT_CONNECTED

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11.04.2024 18:18, kovalev@xxxxxxxxxxxx wrote:
From: Vasiliy Kovalev <kovalev@xxxxxxxxxxxx>

There is no need to drop the connection of some functions in which the
conn->state in BT_CONNECTED is marked, since in the future the same check
takes place (for example, in the hci_encrypt_change_evt() function) and
the hci_conn_drop() is called.

Otherwise, the conn->refcnt will become below zero, which will trigger a
warning and may cause a crash on kernels with the panic_on_warn parameter
enabled.

repro.c generated by syzkaller:

#define _GNU_SOURCE

#include <dirent.h>
#include <endian.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <sched.h>
#include <signal.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/epoll.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>

#include <linux/capability.h>
#include <linux/rfkill.h>

static void sleep_ms(uint64_t ms)
{
        usleep(ms * 1000);
}

static uint64_t current_time_ms(void)
{
        struct timespec ts;
        if (clock_gettime(CLOCK_MONOTONIC, &ts))
        exit(1);
        return (uint64_t)ts.tv_sec * 1000 + (uint64_t)ts.tv_nsec / 1000000;
}

static bool write_file(const char* file, const char* what, ...)
{
        char buf[1024];
        va_list args;
        va_start(args, what);
        vsnprintf(buf, sizeof(buf), what, args);
        va_end(args);
        buf[sizeof(buf) - 1] = 0;
        int len = strlen(buf);
        int fd = open(file, O_WRONLY | O_CLOEXEC);
        if (fd == -1)
                return false;
        if (write(fd, buf, len) != len) {
                int err = errno;
                close(fd);
                errno = err;
                return false;
        }
        close(fd);
        return true;
}

#define MAX_FDS 30

#define BTPROTO_HCI 1
#define ACL_LINK 1
#define SCAN_PAGE 2

typedef struct {
        uint8_t b[6];
} __attribute__((packed)) bdaddr_t;

#define HCI_COMMAND_PKT 1
#define HCI_EVENT_PKT 4
#define HCI_VENDOR_PKT 0xff

struct hci_command_hdr {
        uint16_t opcode;
        uint8_t plen;
} __attribute__((packed));

struct hci_event_hdr {
        uint8_t evt;
        uint8_t plen;
} __attribute__((packed));

#define HCI_EV_CONN_COMPLETE 0x03
struct hci_ev_conn_complete {
        uint8_t status;
        uint16_t handle;
        bdaddr_t bdaddr;
        uint8_t link_type;
        uint8_t encr_mode;
} __attribute__((packed));

#define HCI_EV_CONN_REQUEST 0x04
struct hci_ev_conn_request {
        bdaddr_t bdaddr;
        uint8_t dev_class[3];
        uint8_t link_type;
} __attribute__((packed));

#define HCI_EV_REMOTE_FEATURES 0x0b
struct hci_ev_remote_features {
        uint8_t status;
        uint16_t handle;
        uint8_t features[8];
} __attribute__((packed));

#define HCI_EV_CMD_COMPLETE 0x0e
struct hci_ev_cmd_complete {
        uint8_t ncmd;
        uint16_t opcode;
} __attribute__((packed));

#define HCI_OP_WRITE_SCAN_ENABLE 0x0c1a

#define HCI_OP_READ_BUFFER_SIZE 0x1005
struct hci_rp_read_buffer_size {
        uint8_t status;
        uint16_t acl_mtu;
        uint8_t sco_mtu;
        uint16_t acl_max_pkt;
        uint16_t sco_max_pkt;
} __attribute__((packed));

#define HCI_OP_READ_BD_ADDR 0x1009
struct hci_rp_read_bd_addr {
        uint8_t status;
        bdaddr_t bdaddr;
} __attribute__((packed));

#define HCI_EV_LE_META 0x3e
struct hci_ev_le_meta {
        uint8_t subevent;
} __attribute__((packed));

#define HCI_EV_LE_CONN_COMPLETE 0x01
struct hci_ev_le_conn_complete {
        uint8_t status;
        uint16_t handle;
        uint8_t role;
        uint8_t bdaddr_type;
        bdaddr_t bdaddr;
        uint16_t interval;
        uint16_t latency;
        uint16_t supervision_timeout;
        uint8_t clk_accurancy;
} __attribute__((packed));

struct hci_dev_req {
        uint16_t dev_id;
        uint32_t dev_opt;
};

struct vhci_vendor_pkt {
        uint8_t type;
        uint8_t opcode;
        uint16_t id;
};

#define HCIDEVUP _IOW('H', 201, int)
#define HCISETSCAN _IOW('H', 221, int)

static int vhci_fd = -1;

static void rfkill_unblock_all()
{
        int fd = open("/dev/rfkill", O_WRONLY);
        if (fd < 0)
        exit(1);
        struct rfkill_event event = {0};
        event.idx = 0;
        event.type = RFKILL_TYPE_ALL;
        event.op = RFKILL_OP_CHANGE_ALL;
        event.soft = 0;
        event.hard = 0;
        if (write(fd, &event, sizeof(event)) < 0)
        exit(1);
        close(fd);
}

static void hci_send_event_packet(int fd, uint8_t evt, void* data, size_t data_len)
{
        struct iovec iv[3];
        struct hci_event_hdr hdr;
        hdr.evt = evt;
        hdr.plen = data_len;
        uint8_t type = HCI_EVENT_PKT;
        iv[0].iov_base = &type;
        iv[0].iov_len = sizeof(type);
        iv[1].iov_base = &hdr;
        iv[1].iov_len = sizeof(hdr);
        iv[2].iov_base = data;
        iv[2].iov_len = data_len;
        if (writev(fd, iv, sizeof(iv) / sizeof(struct iovec)) < 0)
        exit(1);
}

static void hci_send_event_cmd_complete(int fd, uint16_t opcode, void* data, size_t data_len)
{
        struct iovec iv[4];
        struct hci_event_hdr hdr;
        hdr.evt = HCI_EV_CMD_COMPLETE;
        hdr.plen = sizeof(struct hci_ev_cmd_complete) + data_len;
        struct hci_ev_cmd_complete evt_hdr;
        evt_hdr.ncmd = 1;
        evt_hdr.opcode = opcode;
        uint8_t type = HCI_EVENT_PKT;
        iv[0].iov_base = &type;
        iv[0].iov_len = sizeof(type);
        iv[1].iov_base = &hdr;
        iv[1].iov_len = sizeof(hdr);
        iv[2].iov_base = &evt_hdr;
        iv[2].iov_len = sizeof(evt_hdr);
        iv[3].iov_base = data;
        iv[3].iov_len = data_len;
        if (writev(fd, iv, sizeof(iv) / sizeof(struct iovec)) < 0)
        exit(1);
}

static bool process_command_pkt(int fd, char* buf, ssize_t buf_size)
{
        struct hci_command_hdr* hdr = (struct hci_command_hdr*)buf;
        if (buf_size < (ssize_t)sizeof(struct hci_command_hdr) ||
            hdr->plen != buf_size - sizeof(struct hci_command_hdr))
        exit(1);
        switch (hdr->opcode) {
        case HCI_OP_WRITE_SCAN_ENABLE: {
                uint8_t status = 0;
hci_send_event_cmd_complete(fd, hdr->opcode, &status, sizeof(status));
                return true;
        }
        case HCI_OP_READ_BD_ADDR: {
                struct hci_rp_read_bd_addr rp = {0};
                rp.status = 0;
                memset(&rp.bdaddr, 0xaa, 6);
hci_send_event_cmd_complete(fd, hdr->opcode, &rp, sizeof(rp));
                return false;
        }
        case HCI_OP_READ_BUFFER_SIZE: {
                struct hci_rp_read_buffer_size rp = {0};
                rp.status = 0;
                rp.acl_mtu = 1021;
                rp.sco_mtu = 96;
                rp.acl_max_pkt = 4;
                rp.sco_max_pkt = 6;
hci_send_event_cmd_complete(fd, hdr->opcode, &rp, sizeof(rp));
                return false;
        }
        }
        char dummy[0xf9] = {0};
        hci_send_event_cmd_complete(fd, hdr->opcode, dummy, sizeof(dummy));
        return false;
}

static void* event_thread(void* arg)
{
        while (1) {
                char buf[1024] = {0};
                ssize_t buf_size = read(vhci_fd, buf, sizeof(buf));
                if (buf_size < 0)
        exit(1);
                if (buf_size > 0 && buf[0] == HCI_COMMAND_PKT) {
if (process_command_pkt(vhci_fd, buf + 1, buf_size - 1))
                                break;
                }
        }
        return NULL;
}
#define HCI_HANDLE_1 200
#define HCI_HANDLE_2 201

static void initialize_vhci()
{
        int hci_sock = socket(AF_BLUETOOTH, SOCK_RAW, BTPROTO_HCI);
        if (hci_sock < 0)
        exit(1);
        vhci_fd = open("/dev/vhci", O_RDWR);
        if (vhci_fd == -1)
        exit(1);
        const int kVhciFd = 202;
        if (dup2(vhci_fd, kVhciFd) < 0)
        exit(1);
        close(vhci_fd);
        vhci_fd = kVhciFd;
        struct vhci_vendor_pkt vendor_pkt;
if (read(vhci_fd, &vendor_pkt, sizeof(vendor_pkt)) != sizeof(vendor_pkt))
        exit(1);
        if (vendor_pkt.type != HCI_VENDOR_PKT)
        exit(1);
        pthread_t th;
        if (pthread_create(&th, NULL, event_thread, NULL))
        exit(1);
        int ret = ioctl(hci_sock, HCIDEVUP, vendor_pkt.id);
        if (ret) {
                if (errno == ERFKILL) {
                        rfkill_unblock_all();
                        ret = ioctl(hci_sock, HCIDEVUP, vendor_pkt.id);
                }
                if (ret && errno != EALREADY)
        exit(1);
        }
        struct hci_dev_req dr = {0};
        dr.dev_id = vendor_pkt.id;
        dr.dev_opt = SCAN_PAGE;
        if (ioctl(hci_sock, HCISETSCAN, &dr))
        exit(1);
        struct hci_ev_conn_request request;
        memset(&request, 0, sizeof(request));
        memset(&request.bdaddr, 0xaa, 6);
        *(uint8_t*)&request.bdaddr.b[5] = 0x10;
        request.link_type = ACL_LINK;
hci_send_event_packet(vhci_fd, HCI_EV_CONN_REQUEST, &request, sizeof(request));
        struct hci_ev_conn_complete complete;
        memset(&complete, 0, sizeof(complete));
        complete.status = 0;
        complete.handle = HCI_HANDLE_1;
        memset(&complete.bdaddr, 0xaa, 6);
        *(uint8_t*)&complete.bdaddr.b[5] = 0x10;
        complete.link_type = ACL_LINK;
        complete.encr_mode = 0;
hci_send_event_packet(vhci_fd, HCI_EV_CONN_COMPLETE, &complete, sizeof(complete));
        struct hci_ev_remote_features features;
        memset(&features, 0, sizeof(features));
        features.status = 0;
        features.handle = HCI_HANDLE_1;
hci_send_event_packet(vhci_fd, HCI_EV_REMOTE_FEATURES, &features, sizeof(features));
        struct {
                struct hci_ev_le_meta le_meta;
                struct hci_ev_le_conn_complete le_conn;
        } le_conn;
        memset(&le_conn, 0, sizeof(le_conn));
        le_conn.le_meta.subevent = HCI_EV_LE_CONN_COMPLETE;
        memset(&le_conn.le_conn.bdaddr, 0xaa, 6);
        *(uint8_t*)&le_conn.le_conn.bdaddr.b[5] = 0x11;
        le_conn.le_conn.role = 1;
        le_conn.le_conn.handle = HCI_HANDLE_2;
hci_send_event_packet(vhci_fd, HCI_EV_LE_META, &le_conn, sizeof(le_conn));
        pthread_join(th, NULL);
        close(hci_sock);
}

static long syz_emit_vhci(volatile long a0, volatile long a1)
{
        if (vhci_fd < 0)
                return (uintptr_t)-1;
        char* data = (char*)a0;
        uint32_t length = a1;
        return write(vhci_fd, data, length);
}

static void setup_common()
{
        if (mount(0, "/sys/fs/fuse/connections", "fusectl", 0, 0)) {
        }
}

static void setup_binderfs()
{
        if (mkdir("/dev/binderfs", 0777)) {
        }
        if (mount("binder", "/dev/binderfs", "binder", 0, NULL)) {
        }
        if (symlink("/dev/binderfs", "./binderfs")) {
        }
}

static void loop();

static void sandbox_common()
{
        prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
        setsid();
        struct rlimit rlim;
        rlim.rlim_cur = rlim.rlim_max = (200 << 20);
        setrlimit(RLIMIT_AS, &rlim);
        rlim.rlim_cur = rlim.rlim_max = 32 << 20;
        setrlimit(RLIMIT_MEMLOCK, &rlim);
        rlim.rlim_cur = rlim.rlim_max = 136 << 20;
        setrlimit(RLIMIT_FSIZE, &rlim);
        rlim.rlim_cur = rlim.rlim_max = 1 << 20;
        setrlimit(RLIMIT_STACK, &rlim);
        rlim.rlim_cur = rlim.rlim_max = 0;
        setrlimit(RLIMIT_CORE, &rlim);
        rlim.rlim_cur = rlim.rlim_max = 256;
        setrlimit(RLIMIT_NOFILE, &rlim);
        if (unshare(CLONE_NEWNS)) {
        }
        if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, NULL)) {
        }
        if (unshare(CLONE_NEWIPC)) {
        }
        if (unshare(0x02000000)) {
        }
        if (unshare(CLONE_NEWUTS)) {
        }
        if (unshare(CLONE_SYSVSEM)) {
        }
        typedef struct {
                const char* name;
                const char* value;
        } sysctl_t;
        static const sysctl_t sysctls[] = {
            {"/proc/sys/kernel/shmmax", "16777216"},
            {"/proc/sys/kernel/shmall", "536870912"},
            {"/proc/sys/kernel/shmmni", "1024"},
            {"/proc/sys/kernel/msgmax", "8192"},
            {"/proc/sys/kernel/msgmni", "1024"},
            {"/proc/sys/kernel/msgmnb", "1024"},
            {"/proc/sys/kernel/sem", "1024 1048576 500 1024"},
        };
        unsigned i;
        for (i = 0; i < sizeof(sysctls) / sizeof(sysctls[0]); i++)
                write_file(sysctls[i].name, sysctls[i].value);
}

static int wait_for_loop(int pid)
{
        if (pid < 0)
        exit(1);
        int status = 0;
        while (waitpid(-1, &status, __WALL) != pid) {
        }
        return WEXITSTATUS(status);
}

static void drop_caps(void)
{
        struct __user_cap_header_struct cap_hdr = {};
        struct __user_cap_data_struct cap_data[2] = {};
        cap_hdr.version = _LINUX_CAPABILITY_VERSION_3;
        cap_hdr.pid = getpid();
        if (syscall(SYS_capget, &cap_hdr, &cap_data))
        exit(1);
        const int drop = (1 << CAP_SYS_PTRACE) | (1 << CAP_SYS_NICE);
        cap_data[0].effective &= ~drop;
        cap_data[0].permitted &= ~drop;
        cap_data[0].inheritable &= ~drop;
        if (syscall(SYS_capset, &cap_hdr, &cap_data))
        exit(1);
}

static int do_sandbox_none(void)
{
        if (unshare(CLONE_NEWPID)) {
        }
        int pid = fork();
        if (pid != 0)
                return wait_for_loop(pid);
        setup_common();
        initialize_vhci();
        sandbox_common();
        drop_caps();
        if (unshare(CLONE_NEWNET)) {
        }
        setup_binderfs();
        loop();
        exit(1);
}

static void kill_and_wait(int pid, int* status)
{
        kill(-pid, SIGKILL);
        kill(pid, SIGKILL);
        for (int i = 0; i < 100; i++) {
                if (waitpid(-1, status, WNOHANG | __WALL) == pid)
                        return;
                usleep(1000);
        }
        DIR* dir = opendir("/sys/fs/fuse/connections");
        if (dir) {
                for (;;) {
                        struct dirent* ent = readdir(dir);
                        if (!ent)
                                break;
if (strcmp(ent->d_name, ".") == 0 || strcmp(ent->d_name, "..") == 0)
                                continue;
                        char abort[300];
snprintf(abort, sizeof(abort), "/sys/fs/fuse/connections/%s/abort", ent->d_name);
                        int fd = open(abort, O_WRONLY);
                        if (fd == -1) {
                                continue;
                        }
                        if (write(fd, abort, 1) < 0) {
                        }
                        close(fd);
                }
                closedir(dir);
        } else {
        }
        while (waitpid(-1, status, __WALL) != pid) {
        }
}

static void setup_test()
{
        prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
        setpgrp();
        write_file("/proc/self/oom_score_adj", "1000");
}

static void close_fds()
{
        for (int fd = 3; fd < MAX_FDS; fd++)
                close(fd);
}

static void execute_one(void);

#define WAIT_FLAGS __WALL

static void loop(void)
{
        int iter = 0;
        for (;; iter++) {
                int pid = fork();
                if (pid < 0)
        exit(1);
                if (pid == 0) {
                        setup_test();
                        execute_one();
                        close_fds();
                        exit(0);
                }
                int status = 0;
                uint64_t start = current_time_ms();
                for (;;) {
if (waitpid(-1, &status, WNOHANG | WAIT_FLAGS) == pid)
                                break;
                        sleep_ms(1);
                        if (current_time_ms() - start < 5000)
                                continue;
                        kill_and_wait(pid, &status);
                        break;
                }
        }
}

void execute_one(void)
{
*(uint8_t*)0x20000040 = 4;
*(uint8_t*)0x20000041 = 8;
*(uint8_t*)0x20000042 = 4;
*(uint8_t*)0x20000043 = 0xf9;
*(uint16_t*)0x20000044 = 0xc8;
*(uint8_t*)0x20000046 = 2;
syz_emit_vhci(0x20000040, 7);

}
int main(void)
{
syscall(__NR_mmap, 0x1ffff000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul); syscall(__NR_mmap, 0x20000000ul, 0x1000000ul, 7ul, 0x32ul, -1, 0ul);
        syscall(__NR_mmap, 0x21000000ul, 0x1000ul, 0ul, 0x32ul, -1, 0ul);
                        do_sandbox_none();
        return 0;
}

--
Regards,
Vasiliy Kovalev




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