From e755f780865221252ef3321215c9796b78e7b1c5 Mon Sep 17 00:00:00 2001 From: Anand Jain Date: Mon, 30 Jun 2014 17:12:47 +0800 Subject: [PATCH] btrfs: fix null pointer dereference in clone_fs_devices when name is null when one of the device path is missing btrfs_device name is null. So this patch will check for that. stack: BUG: unable to handle kernel NULL pointer dereference at 0000000000000010 IP: [] strlen+0x0/0x30 [] ? clone_fs_devices+0xaa/0x160 [btrfs] [] btrfs_init_new_device+0x317/0xca0 [btrfs] [] ? __kmalloc_track_caller+0x15a/0x1a0 [] btrfs_ioctl+0xaa3/0x2860 [btrfs] [] ? handle_mm_fault+0x48c/0x9c0 [] ? __blkdev_put+0x171/0x180 [] ? __do_page_fault+0x4ac/0x590 [] ? blkdev_put+0x106/0x110 [] ? mntput+0x35/0x40 [] do_vfs_ioctl+0x460/0x4a0 [] ? ____fput+0xe/0x10 [] ? task_work_run+0xb3/0xd0 [] SyS_ioctl+0x57/0x90 [] ? do_page_fault+0xe/0x10 [] system_call_fastpath+0x16/0x1b reproducer: mkfs.btrfs -draid1 -mraid1 /dev/sdg1 /dev/sdg2 btrfstune -S 1 /dev/sdg1 modprobe -r btrfs && modprobe btrfs mount -o degraded /dev/sdg1 /btrfs btrfs dev add /dev/sdg3 /btrfs Signed-off-by: Anand Jain Signed-off-by: Chris Mason --- fs/btrfs/volumes.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 6ca0d9cc46f9..6104676857f5 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -555,12 +555,14 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig) * This is ok to do without rcu read locked because we hold the * uuid mutex so nothing we touch in here is going to disappear. */ - name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS); - if (!name) { - kfree(device); - goto error; + if (orig_dev->name) { + name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS); + if (!name) { + kfree(device); + goto error; + } + rcu_assign_pointer(device->name, name); } - rcu_assign_pointer(device->name, name); list_add(&device->dev_list, &fs_devices->devices); device->fs_devices = fs_devices;