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authorTyler Hicks <tyhicks@linux.vnet.ibm.com>2009-09-22 12:52:17 -0500
committerTyler Hicks <tyhicks@linux.vnet.ibm.com>2009-09-23 09:10:34 -0500
commit9c2d2056647790c5034d722bd24e9d913ebca73c (patch)
tree38db96956ac0167b2a277429746c500b522bc5aa /fs/ecryptfs
parent96a7b9c2f5df899f302ade45cf17ad753fe130fd (diff)
eCryptfs: Prevent lower dentry from going negative during unlink
When calling vfs_unlink() on the lower dentry, d_delete() turns the dentry into a negative dentry when the d_count is 1. This eventually caused a NULL pointer deref when a read() or write() was done and the negative dentry's d_inode was dereferenced in ecryptfs_read_update_atime() or ecryptfs_getxattr(). Placing mutt's tmpdir in an eCryptfs mount is what initially triggered the oops and I was able to reproduce it with the following sequence: open("/tmp/upper/foo", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600) = 3 link("/tmp/upper/foo", "/tmp/upper/bar") = 0 unlink("/tmp/upper/foo") = 0 open("/tmp/upper/bar", O_RDWR|O_CREAT|O_NOFOLLOW, 0600) = 4 unlink("/tmp/upper/bar") = 0 write(4, "eCryptfs test\n"..., 14 <unfinished ...> +++ killed by SIGKILL +++ https://bugs.launchpad.net/ecryptfs/+bug/387073 Reported-by: Loïc Minier <loic.minier@canonical.com> Cc: Serge Hallyn <serue@us.ibm.com> Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com> Cc: ecryptfs-devel@lists.launchpad.net Cc: stable <stable@kernel.org> Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Diffstat (limited to 'fs/ecryptfs')
-rw-r--r--fs/ecryptfs/inode.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 2f0945d63297..056fed62d0de 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -476,6 +476,7 @@ static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry)
struct inode *lower_dir_inode = ecryptfs_inode_to_lower(dir);
struct dentry *lower_dir_dentry;
+ dget(lower_dentry);
lower_dir_dentry = lock_parent(lower_dentry);
rc = vfs_unlink(lower_dir_inode, lower_dentry);
if (rc) {
@@ -489,6 +490,7 @@ static int ecryptfs_unlink(struct inode *dir, struct dentry *dentry)
d_drop(dentry);
out_unlock:
unlock_dir(lower_dir_dentry);
+ dput(lower_dentry);
return rc;
}