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f4e19e595c
linux/fs/overlayfs
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Zhihao Cheng f4e19e595c ovl: fix null pointer dereference in ovl_get_acl_rcu() 
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.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=217404
Fixes: 332f606b32 ("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>
2023-06-19 14:01:12 +03:00
..
copy_up.c ovl: check for ->listxattr() support 2023-03-06 09:57:13 +01:00
dir.c fs: port inode_init_owner() to mnt_idmap 2023-01-19 09:24:28 +01:00
export.c fs: port ->permission() to pass mnt_idmap 2023-01-19 09:24:28 +01:00
file.c fs: port inode_owner_or_capable() to mnt_idmap 2023-01-19 09:24:29 +01:00
inode.c ovl: fix null pointer dereference in ovl_get_acl_rcu() 2023-06-19 14:01:12 +03:00
Kconfig ovl: Kconfig: Fix spelling mistake "undelying" -> "underlying" 2022-12-08 10:49:46 +01:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
namei.c fs: port ->permission() to pass mnt_idmap 2023-01-19 09:24:28 +01:00
overlayfs.h ovl: let helper ovl_i_path_real() return the realinode 2023-06-19 14:00:38 +03:00
ovl_entry.h fs: port ->permission() to pass mnt_idmap 2023-01-19 09:24:28 +01:00
readdir.c fs: port ->permission() to pass mnt_idmap 2023-01-19 09:24:28 +01:00
super.c fs: drop unused posix acl handlers 2023-03-06 09:57:12 +01:00
util.c ovl: let helper ovl_i_path_real() return the realinode 2023-06-19 14:00:38 +03:00