CVE-2023-53260

In the Linux kernel, the following vulnerability has been resolved:

ovl: fix null pointer dereference in ovl_permission()

Following process: P1 P2 pathlookupat linkpathwalk inodepermission ovlpermission ovlipathreal(inode, &realpath) path->dentry = ovlidentryupper(inode) dropcache dentrykill(ovldentry) iput(ovlinode) ovldestroyinode(ovlinode) dput(oi->upperdentry) dentrykill(upperdentry) dentryunlinkinode upperdentry->dinode = NULL realinode = dinode(realpath.dentry) // return NULL inodepermission(realinode) inode->isb // NULL pointer dereference , will trigger an null pointer dereference at realinode: [ 335.664979] BUG: kernel NULL pointer dereference, address: 0000000000000002 [ 335.668032] CPU: 0 PID: 2592 Comm: ls Not tainted 6.3.0 [ 335.669956] RIP: 0010:inodepermission+0x33/0x2c0 [ 335.678939] Call Trace: [ 335.679165] <TASK> [ 335.679371] ovlpermission+0xde/0x320 [ 335.679723] inodepermission+0x15e/0x2c0 [ 335.680090] linkpathwalk+0x115/0x550 [ 335.680771] pathlookupat.isra.0+0xb2/0x200 [ 335.681170] filenamelookup+0xda/0x240 [ 335.681922] vfsstatx+0xa6/0x1f0 [ 335.682233] vfsfstatat+0x7b/0xb0

Fetch a reproducer in [Link].

Use the helper ovlipath_realinode() to get realinode and then do non-nullptr checking.