From 45ea6095c8f0d6caad5658306416a5d254f1205e Mon Sep 17 00:00:00 2001 From: "slyich@gmail.com" Date: Mon, 7 Nov 2011 16:08:01 -0500 Subject: [PATCH] btrfs: fix double-free 'tree_root' in 'btrfs_mount()' On error path 'tree_root' is treed in 'free_fs_info()'. No need to free it explicitely. Noticed by SLUB in debug mode: Complete reproducer under usermode linux (discovered on real machine): bdev=/dev/ubda btr_root=/btr /mkfs.btrfs $bdev mount $bdev $btr_root mkdir $btr_root/subvols/ cd $btr_root/subvols/ /btrfs su cr foo /btrfs su cr bar mount $bdev -osubvol=subvols/foo $btr_root/subvols/bar umount $btr_root/subvols/bar which gives device fsid 4d55aa28-45b1-474b-b4ec-da912322195e devid 1 transid 7 /dev/ubda ============================================================================= BUG kmalloc-2048: Object already free ----------------------------------------------------------------------------- INFO: Allocated in btrfs_mount+0x389/0x7f0 age=0 cpu=0 pid=277 INFO: Freed in btrfs_mount+0x51c/0x7f0 age=0 cpu=0 pid=277 INFO: Slab 0x0000000062886200 objects=15 used=9 fp=0x0000000070b4d2d0 flags=0x4081 INFO: Object 0x0000000070b4d2d0 @offset=21200 fp=0x0000000070b4a968 ... Call Trace: 70b31948: [<6008c522>] print_trailer+0xe2/0x130 70b31978: [<6008c5aa>] object_err+0x3a/0x50 70b319a8: [<6008e242>] free_debug_processing+0x142/0x2a0 70b319e0: [<600ebf6f>] btrfs_mount+0x55f/0x7f0 70b319f8: [<6008e5c1>] __slab_free+0x221/0x2d0 Signed-off-by: Sergei Trofimovich Cc: Arne Jansen Cc: Chris Mason Cc: David Sterba Signed-off-by: Chris Mason --- fs/btrfs/super.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 57080dffdfc..dcd5aef6b61 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -933,8 +933,12 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, * then open_ctree will properly initialize everything later. */ fs_info = kzalloc(sizeof(struct btrfs_fs_info), GFP_NOFS); + if (!fs_info) { + error = -ENOMEM; + goto error_close_devices; + } tree_root = kzalloc(sizeof(struct btrfs_root), GFP_NOFS); - if (!fs_info || !tree_root) { + if (!tree_root) { error = -ENOMEM; goto error_close_devices; } @@ -964,7 +968,6 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, btrfs_close_devices(fs_devices); free_fs_info(fs_info); - kfree(tree_root); } else { char b[BDEVNAME_SIZE]; @@ -992,7 +995,6 @@ static struct dentry *btrfs_mount(struct file_system_type *fs_type, int flags, error_close_devices: btrfs_close_devices(fs_devices); free_fs_info(fs_info); - kfree(tree_root); return ERR_PTR(error); } -- 2.20.1