From: Vasiliy Kovalev kovalev@altlinux.org

[ Upstream commit c84e125fff2615b4d9c259e762596134eddd2f27 ]

The issue was caused by dput(upper) being called before ovl_dentry_update_reval(), while upper->d_flags was still accessed in ovl_dentry_remote().

Move dput(upper) after its last use to prevent use-after-free.

BUG: KASAN: slab-use-after-free in ovl_dentry_remote fs/overlayfs/util.c:162 [inline] BUG: KASAN: slab-use-after-free in ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167

Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:114 print_address_description mm/kasan/report.c:377 [inline] print_report+0xc3/0x620 mm/kasan/report.c:488 kasan_report+0xd9/0x110 mm/kasan/report.c:601 ovl_dentry_remote fs/overlayfs/util.c:162 [inline] ovl_dentry_update_reval+0xd2/0xf0 fs/overlayfs/util.c:167 ovl_link_up fs/overlayfs/copy_up.c:610 [inline] ovl_copy_up_one+0x2105/0x3490 fs/overlayfs/copy_up.c:1170 ovl_copy_up_flags+0x18d/0x200 fs/overlayfs/copy_up.c:1223 ovl_rename+0x39e/0x18c0 fs/overlayfs/dir.c:1136 vfs_rename+0xf84/0x20a0 fs/namei.c:4893 ... </TASK>

Fixes: b07d5cc93e1b ("ovl: update of dentry revalidate flags after copy up") Reported-by: syzbot+316db8a1191938280eb6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=316db8a1191938280eb6 Signed-off-by: Vasiliy Kovalev kovalev@altlinux.org Link: https://lore.kernel.org/r/20250214215148.761147-1-kovalev@altlinux.org Reviewed-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Christian Brauner brauner@kernel.org [ Minor context change fixed. ] Signed-off-by: Bin Lan lanbincn@qq.com --- fs/overlayfs/copy_up.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 65ac504595ba..a1ec45fc77d8 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -469,7 +469,6 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c) err = PTR_ERR(upper); if (!IS_ERR(upper)) { err = ovl_do_link(ovl_dentry_upper(c->dentry), udir, upper); - dput(upper);

if (!err) { /* Restore timestamps on parent (best effort) */ @@ -477,6 +476,7 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c) ovl_dentry_set_upper_alias(c->dentry); ovl_dentry_update_reval(c->dentry, upper); } + dput(upper); } inode_unlock(udir); if (err)