CVE-2025-21887

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ovl: fix UAF in ovl_dentry_update_reval by moving dput() in ovl_link_up<br /> <br /> The issue was caused by dput(upper) being called before<br /> ovl_dentry_update_reval(), while upper-&gt;d_flags was still<br /> accessed in ovl_dentry_remote().<br /> <br /> Move dput(upper) after its last use to prevent use-after-free.<br /> <br /> BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline]<br /> BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167<br /> <br /> Call Trace:<br /> <br /> __dump_stack lib/dump_stack.c:88 [inline]<br /> dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114<br /> print_address_description mm/kasan/report.c:377 [inline]<br /> print_report+0xc3/0x620 mm/kasan/report.c:488<br /> kasan_report+0xd9/0x110 mm/kasan/report.c:601<br /> ovl_dentry_remote fs/overlayfs/util.c:162 [inline]<br /> ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167<br /> ovl_link_up fs/overlayfs/copy_up.c:610 [inline]<br /> ovl_copy_up_one+0x2105/0x3490 fs/overlayfs/copy_up.c:1170<br /> ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223<br /> ovl_rename+0x39e/0x18c0 fs/overlayfs/dir.c:1136<br /> vfs_rename+0xf84/0x20a0 fs/namei.c:4893<br /> ...<br />