From: Ye Bin yebin10@huawei.com
mainline inclusion from mainline-v5.16 commit 0c98057be9efa32de78dbc4685fc73da9d71faa1 category: bugfix bugzilla: 182875 https://gitee.com/openeuler/kernel/issues/I4DDEL
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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I got issue as follows: [ 263.886511] BUG: KASAN: use-after-free in pid_show+0x11f/0x13f [ 263.888359] Read of size 4 at addr ffff8880bf0648c0 by task cat/746 [ 263.890479] CPU: 0 PID: 746 Comm: cat Not tainted 4.19.90-dirty #140 [ 263.893162] Call Trace: [ 263.893509] dump_stack+0x108/0x15f [ 263.893999] print_address_description+0xa5/0x372 [ 263.894641] kasan_report.cold+0x236/0x2a8 [ 263.895696] __asan_report_load4_noabort+0x25/0x30 [ 263.896365] pid_show+0x11f/0x13f [ 263.897422] dev_attr_show+0x48/0x90 [ 263.898361] sysfs_kf_seq_show+0x24d/0x4b0 [ 263.899479] kernfs_seq_show+0x14e/0x1b0 [ 263.900029] seq_read+0x43f/0x1150 [ 263.900499] kernfs_fop_read+0xc7/0x5a0 [ 263.903764] vfs_read+0x113/0x350 [ 263.904231] ksys_read+0x103/0x270 [ 263.905230] __x64_sys_read+0x77/0xc0 [ 263.906284] do_syscall_64+0x106/0x360 [ 263.906797] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Reproduce this issue as follows: 1. nbd-server 8000 /tmp/disk 2. nbd-client localhost 8000 /dev/nbd1 3. cat /sys/block/nbd1/pid Then trigger use-after-free in pid_show.
Reason is after do step '2', nbd-client progress is already exit. So it's task_struct already freed. To solve this issue, revert part of 6521d39a64b3's modify and remove useless 'recv_task' member of nbd_device.
Fixes: 6521d39a64b3 ("nbd: Remove variable 'pid'") Signed-off-by: Ye Bin yebin10@huawei.com Reviewed-by: Josef Bacik josef@toxicpanda.com Link: https://lore.kernel.org/r/20211020073959.2679255-1-yebin10@huawei.com Signed-off-by: Jens Axboe axboe@kernel.dk
conflicts: drivers/block/nbd.c
Signed-off-by: Ye Bin yebin10@huawei.com Reviewed-by: Jason Yan yanaijie@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- drivers/block/nbd.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index fe635bc3e8c4..bb50af20b284 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -114,11 +114,11 @@ struct nbd_device { struct workqueue_struct *recv_workq;
struct list_head list; - struct task_struct *task_recv; struct task_struct *task_setup;
struct completion *destroy_complete; unsigned long flags; + pid_t pid; /* pid of nbd-client, if attached */ };
#define NBD_CMD_REQUEUED 1 @@ -214,7 +214,7 @@ static ssize_t pid_show(struct device *dev, struct gendisk *disk = dev_to_disk(dev); struct nbd_device *nbd = (struct nbd_device *)disk->private_data;
- return sprintf(buf, "%d\n", task_pid_nr(nbd->task_recv)); + return sprintf(buf, "%d\n", nbd->pid); }
static const struct device_attribute pid_attr = { @@ -333,7 +333,7 @@ static void nbd_size_set(struct nbd_device *nbd, loff_t blocksize, struct nbd_config *config = nbd->config; config->blksize = blocksize; config->bytesize = blocksize * nr_blocks; - if (nbd->task_recv != NULL) + if (nbd->pid) nbd_size_update(nbd, false); }
@@ -1284,7 +1284,7 @@ static void nbd_config_put(struct nbd_device *nbd) if (test_and_clear_bit(NBD_RT_HAS_PID_FILE, &config->runtime_flags)) device_remove_file(disk_to_dev(nbd->disk), &pid_attr); - nbd->task_recv = NULL; + nbd->pid = 0; nbd_clear_sock(nbd); if (config->num_connections) { int i; @@ -1319,7 +1319,7 @@ static int nbd_start_device(struct nbd_device *nbd) int num_connections = config->num_connections; int error = 0, i;
- if (nbd->task_recv) + if (nbd->pid) return -EBUSY; if (!config->socks) return -EINVAL; @@ -1338,7 +1338,7 @@ static int nbd_start_device(struct nbd_device *nbd) }
blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections); - nbd->task_recv = current; + nbd->pid = task_pid_nr(current);
nbd_parse_flags(nbd);
@@ -1612,8 +1612,8 @@ static int nbd_dbg_tasks_show(struct seq_file *s, void *unused) { struct nbd_device *nbd = s->private;
- if (nbd->task_recv) - seq_printf(s, "recv: %d\n", task_pid_nr(nbd->task_recv)); + if (nbd->pid) + seq_printf(s, "recv: %d\n", nbd->pid);
return 0; } @@ -2188,7 +2188,7 @@ static int nbd_genl_reconfigure(struct sk_buff *skb, struct genl_info *info) mutex_lock(&nbd->config_lock); config = nbd->config; if (!test_bit(NBD_RT_BOUND, &config->runtime_flags) || - !nbd->task_recv) { + !nbd->pid) { dev_err(nbd_to_dev(nbd), "not configured, cannot reconfigure\n"); ret = -EINVAL;