Commit 0aeb8a6e authored by Anand Jain's avatar Anand Jain Committed by Chris Mason

btrfs: fix null pointer dereference in btrfs_show_devname when name is null

dev->name is null but missing flag is not set.
Strictly speaking the missing flag should have been set, but there
are more places where code just checks if name is null. For now this
patch does the same.

stack:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000064
IP: [<ffffffffa0228908>] btrfs_show_devname+0x58/0xf0 [btrfs]

[<ffffffff81198879>] show_vfsmnt+0x39/0x130
[<ffffffff81178056>] m_show+0x16/0x20
[<ffffffff8117d706>] seq_read+0x296/0x390
[<ffffffff8115aa7d>] vfs_read+0x9d/0x160
[<ffffffff8115b549>] SyS_read+0x49/0x90
[<ffffffff817abe52>] 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: default avatarAnand Jain <Anand.Jain@oracle.com>
Signed-off-by: default avatarChris Mason <clm@fb.com>
parent e755f780
......@@ -1811,6 +1811,8 @@ static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
list_for_each_entry(dev, head, dev_list) {
if (dev->missing)
continue;
if (!dev->name)
continue;
if (!first_dev || dev->devid < first_dev->devid)
first_dev = dev;
}
......
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