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Subject[18/91] nilfs2: fix list corruption after ifile creation failure
2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

commit af4e36318edb848fcc0a8d5f75000ca00cdc7595 upstream.

If nilfs_attach_checkpoint() gets a memory allocation failure during
creation of ifile, it will return without removing nilfs_sb_info
struct from ns_supers list. When a concurrently mounted snapshot is
unmounted or another new snapshot is mounted after that, this causes
kernel oops as below:

> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<f83662ff>] nilfs_find_sbinfo+0x74/0xa4 [nilfs2]
> *pde = 00000000
> Oops: 0000 [#1] SMP
<snip>
> Call Trace:
> [<f835dc29>] ? nilfs_get_sb+0x165/0x532 [nilfs2]
> [<c1173c87>] ? ida_get_new_above+0x16d/0x187
> [<c109a7f8>] ? alloc_vfsmnt+0x7e/0x10a
> [<c1070790>] ? kstrdup+0x2c/0x40
> [<c1089041>] ? vfs_kern_mount+0x96/0x14e
> [<c108913d>] ? do_kern_mount+0x32/0xbd
> [<c109b331>] ? do_mount+0x642/0x6a1
> [<c101a415>] ? do_page_fault+0x0/0x2d1
> [<c1099c00>] ? copy_mount_options+0x80/0xe2
> [<c10705d8>] ? strndup_user+0x48/0x67
> [<c109b3f1>] ? sys_mount+0x61/0x90
> [<c10027cc>] ? sysenter_do_call+0x12/0x22

This fixes the problem.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nilfs2/super.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -360,9 +360,10 @@ int nilfs_attach_checkpoint(struct nilfs
list_add(&sbi->s_list, &nilfs->ns_supers);
up_write(&nilfs->ns_super_sem);

+ err = -ENOMEM;
sbi->s_ifile = nilfs_ifile_new(sbi, nilfs->ns_inode_size);
if (!sbi->s_ifile)
- return -ENOMEM;
+ goto delist;

down_read(&nilfs->ns_segctor_sem);
err = nilfs_cpfile_get_checkpoint(nilfs->ns_cpfile, cno, 0, &raw_cp,
@@ -393,6 +394,7 @@ int nilfs_attach_checkpoint(struct nilfs
nilfs_mdt_destroy(sbi->s_ifile);
sbi->s_ifile = NULL;

+ delist:
down_write(&nilfs->ns_super_sem);
list_del_init(&sbi->s_list);
up_write(&nilfs->ns_super_sem);



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