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

From: kovalev
Date: Thu Apr 11 2024 - 11:36:14 EST

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In reply to: kovalev: "[PATCH net] Bluetooth: hci_event: fix double hci_conn_drop() when conn->state == BT_CONNECTED"
Next in thread: Luiz Augusto von Dentz: "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

Next message: Jens Axboe: "[PATCH 007/437] mm/util: add iterdup_nul() and iterdup() helpers"
Previous message: Jens Axboe: "[PATCH 002/437] fs: add generic read/write iterator helpers"
In reply to: kovalev: "[PATCH net] Bluetooth: hci_event: fix double hci_conn_drop() when conn->state == BT_CONNECTED"
Next in thread: Luiz Augusto von Dentz: "Re: [PATCH net] Bluetooth: hci_event: fix double hci_conn_drop() when conn->state == BT_CONNECTED"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]