Please have a look at the following patch fixing locking in proc_check_root().
It brings is_subdir() call under vfsmount_lock. Holding vfsmount_lock will
ensure mnt_mountpoint dentry is intact and the dentry does not go away while
it is being checked in is_subdir().
fs/proc/base.c | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)
diff -puN fs/proc/base.c~proc_check_root-fix-locking fs/proc/base.c
--- linux-2.6.2-rc2/fs/proc/base.c~proc_check_root-fix-locking 2004-01-27 22:28:07.000000000 +0530
+++ linux-2.6.2-rc2-maneesh/fs/proc/base.c 2004-01-27 22:28:07.000000000 +0530
@@ -425,17 +425,15 @@ static int proc_check_root(struct inode
mnt = vfsmnt;
while (vfsmnt != our_vfsmnt) {
- if (vfsmnt == vfsmnt->mnt_parent) {
- spin_unlock(&vfsmount_lock);
+ if (vfsmnt == vfsmnt->mnt_parent)
goto out;
- }
de = vfsmnt->mnt_mountpoint;
vfsmnt = vfsmnt->mnt_parent;
}
- spin_unlock(&vfsmount_lock);
if (!is_subdir(de, base))
goto out;
+ spin_unlock(&vfsmount_lock);
exit:
dput(base);
@@ -444,6 +442,7 @@ exit:
mntput(mnt);
return res;
out:
+ spin_unlock(&vfsmount_lock);
res = -EACCES;
goto exit;
}
_
--
Maneesh Soni
Linux Technology Center,
IBM Software Lab, Bangalore, India
email: [email protected]
Phone: 91-80-5044999 Fax: 91-80-5268553
T/L : 9243696