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    SubjectRe: 2.6.23-rc7-mm1 - 'touch' command causes Oops.
    On Mon, Sep 24, 2007 at 06:35:50AM -0400, Valdis.Kletnieks@vt.edu wrote:
    > On Mon, 24 Sep 2007 02:17:16 PDT, Andrew Morton said:
    >
    > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc7/2.6.23-rc7-mm1/
    >
    > It lived fast, it died young, it didn't leave a pretty corpse...
    >
    > Something in the startup scripts did a 'touch', and ker-blam.
    > [ 15.668000] Call Trace:
    > [ 15.668000] [<ffffffff802a4d20>] mnt_want_write+0x49/0xb5
    > [ 15.668000] [<ffffffff802ad288>] do_utimes+0xd0/0x220
    > [ 15.668000] [<ffffffff8035437b>] __up_read+0x7a/0x83
    > [ 15.668000] [<ffffffff8024b1af>] up_read+0x9/0xb
    > [ 15.668000] [<ffffffff8051977c>] do_page_fault+0x421/0x7d0
    > [ 15.668000] [<ffffffff8028b370>] do_filp_open+0x36/0x46
    > [ 15.668000] [<ffffffff802ad519>] sys_utimensat+0x8b/0xa5
    > [ 15.668000] [<ffffffff80517a4d>] error_exit+0x0/0x84
    > [ 15.668000] [<ffffffff8020c10e>] system_call+0x7e/0x83

    do_times passes an unitialized vfsmount into mnt_want_write. Here's
    the quick fix (untested), but the right fix is to restructure the complete
    mess do_utimes is (never let a libc developer write your kernel code.. :)):


    Index: linux-2.6.23-rc6/fs/utimes.c
    ===================================================================
    --- linux-2.6.23-rc6.orig/fs/utimes.c 2007-09-24 14:02:24.000000000 +0200
    +++ linux-2.6.23-rc6/fs/utimes.c 2007-09-24 14:03:57.000000000 +0200
    @@ -59,6 +59,7 @@ long do_utimes(int dfd, char __user *fil
    struct inode *inode;
    struct iattr newattrs;
    struct file *f = NULL;
    + struct vfsmount *mnt;

    error = -EINVAL;
    if (times && (!nsec_valid(times[0].tv_nsec) ||
    @@ -79,17 +80,19 @@ long do_utimes(int dfd, char __user *fil
    if (!f)
    goto out;
    dentry = f->f_path.dentry;
    + mnt = f->f_path.mnt;
    } else {
    error = __user_walk_fd(dfd, filename, (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW, &nd);
    if (error)
    goto out;

    dentry = nd.dentry;
    + mnt = nd.mnt;
    }

    inode = dentry->d_inode;

    - error = mnt_want_write(nd.mnt);
    + error = mnt_want_write(mnt);
    if (error)
    goto dput_and_out;


    -
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