[223/272] nilfs2: fix crash after one superblock became unavailable

Greg KH
2011-02-16T00:24:48Z

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

commit 0ca7a5b9ac5d301845dd6382ff25a699b6263a81 upstream.

Fixes the following kernel oops in nilfs_setup_super() which could
arise if one of two super-blocks is unavailable.

> BUG: unable to handle kernel NULL pointer dereference at (null)
> Pid: 3529, comm: mount.nilfs2 Not tainted 2.6.37 #1 /
> EIP: 0060:[<c03196bc>] EFLAGS: 00010202 CPU: 3
> EIP is at memcpy+0xc/0x1b
> Call Trace:
> [<f953720e>] ? nilfs_setup_super+0x6c/0xa5 [nilfs2]
> [<f95369e9>] ? nilfs_get_root_dentry+0x81/0xcb [nilfs2]
> [<f9537a08>] ? nilfs_mount+0x4f9/0x62c [nilfs2]
> [<c02745cf>] ? kstrdup+0x36/0x3f
> [<f953750f>] ? nilfs_mount+0x0/0x62c [nilfs2]
> [<c0293940>] ? vfs_kern_mount+0x4d/0x12c
> [<c02a5100>] ? get_fs_type+0x76/0x8f
> [<c0293a68>] ? do_kern_mount+0x33/0xbf
> [<c02a784a>] ? do_mount+0x2ed/0x714
> [<c02a6171>] ? copy_mount_options+0x28/0xfc
> [<c02a7ce3>] ? sys_mount+0x72/0xaf
> [<c0473085>] ? syscall_call+0x7/0xb

Reported-by: Wakko Warner <wakko@animx.eu.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Wakko Warner <wakko@animx.eu.org>
LKML-Reference: <20110121024918.GA29598@animx.eu.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nilfs2/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -688,7 +688,8 @@ skip_mount_setup:
sbp[0]->s_state =
cpu_to_le16(le16_to_cpu(sbp[0]->s_state) & ~NILFS_VALID_FS);
/* synchronize sbp[1] with sbp[0] */
- memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
+ if (sbp[1])
+ memcpy(sbp[1], sbp[0], nilfs->ns_sbsize);
return nilfs_commit_super(sbi, NILFS_SB_COMMIT_ALL);
}