On Mon, Jul 10, 2023 at 6:29 AM Zhihao Cheng chengzhihao1@huawei.com wrote:
[ Upstream commit f4e19e595cc2e76a8a58413eb19d3d9c51328b53 ]
Following process: P1 P2 path_openat link_path_walk may_lookup inode_permission(rcu) ovl_permission acl_permission_check check_acl get_cached_acl_rcu ovl_get_inode_acl realinode = ovl_inode_real(ovl_inode) drop_cache __dentry_kill(ovl_dentry) iput(ovl_inode) ovl_destroy_inode(ovl_inode) dput(oi->__upperdentry) dentry_kill(upperdentry) dentry_unlink_inode upperdentry->d_inode = NULL ovl_inode_upper upperdentry = ovl_i_dentry_upper(ovl_inode) d_inode(upperdentry) // returns NULL IS_POSIXACL(realinode) // NULL pointer dereference , will trigger an null pointer dereference at realinode: [ 205.472797] BUG: kernel NULL pointer dereference, address: 0000000000000028 [ 205.476701] CPU: 2 PID: 2713 Comm: ls Not tainted 6.3.0-12064-g2edfa098e750-dirty #1216 [ 205.478754] RIP: 0010:do_ovl_get_acl+0x5d/0x300 [ 205.489584] Call Trace: [ 205.489812] <TASK> [ 205.490014] ovl_get_inode_acl+0x26/0x30 [ 205.490466] get_cached_acl_rcu+0x61/0xa0 [ 205.490908] generic_permission+0x1bf/0x4e0 [ 205.491447] ovl_permission+0x79/0x1b0 [ 205.491917] inode_permission+0x15e/0x2c0 [ 205.492425] link_path_walk+0x115/0x550 [ 205.493311] path_lookupat.isra.0+0xb2/0x200 [ 205.493803] filename_lookup+0xda/0x240 [ 205.495747] vfs_fstatat+0x7b/0xb0
Fetch a reproducer in [Link].
Use the helper ovl_i_path_realinode() to get realinode and then do non-nullptr checking.
There are some changes from upstream commit:
- Corrusponds to do_ovl_get_acl() in 5.15 is ovl_get_acl()
- ovl_i_path_real is not imported in 5.15, we can get realinode by ovl_inode_real
- CONFIG_FS_POSIX_ACL checking is dropped in commit ded536561a3674327dfa4bb389085705cae22b8a ("ovl: improve ovl_get_acl() if POSIX ACL support is off"), we still keep it in 5.15.
Zhihao,
Can you please provide also the backport for 6.1.
Basically, the same as this one without the CONFIG_FS_POSIX_ACL check.
Thanks, Amir.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217404 Fixes: 332f606b32b6 ("ovl: enable RCU'd ->get_acl()") Cc: stable@vger.kernel.org # v5.15 Signed-off-by: Zhihao Cheng chengzhihao1@huawei.com Suggested-by: Christian Brauner brauner@kernel.org Suggested-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com
fs/overlayfs/inode.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index d41f0c8e0e2a..65e5e6eb761a 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -453,7 +453,15 @@ struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu) const struct cred *old_cred; struct posix_acl *acl;
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL))return NULL;if (!realinode) {WARN_ON(!rcu);return ERR_PTR(-ECHILD);}if (!IS_POSIXACL(realinode)) return NULL; if (rcu)-- 2.39.2