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@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=316db8a1191938280eb6
Signed-off-by: Vasiliy Kovalev <kovalev@xxxxxxxxxxxx>
---
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 0c28e5fa34077..d7310fcf38881 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -618,7 +618,6 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c)
err = PTR_ERR(upper);
if (!IS_ERR(upper)) {
err = ovl_do_link(ofs, ovl_dentry_upper(c->dentry), udir, upper);
- dput(upper);
if (!err) {
/* Restore timestamps on parent (best effort) */
@@ -626,6 +625,7 @@ 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)
--
2.42.2
