mainline inclusion from mainline-v7.3-rc3 commit f06c2d26d1999d37e93299db0ecead04ca7d0b9f category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19854 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- configfs_get_config_item() treats a hashed dentry as proof that sd->s_element is a live config_item. configfs_rmdir() breaks that: simple_rmdir() leaves the dentry hashed, the last reference to the item is dropped right after, and the dentry is only unhashed by d_delete() once ->rmdir() has returned. configfs_symlink() resolves its target holding no lock on it, so get_target() can land in that window: BUG: KASAN: slab-use-after-free in config_item_get+0x26/0x90 get_target fs/configfs/symlink.c:128 [inline] configfs_symlink+0x4ab/0x1030 fs/configfs/symlink.c:185 Unhash in configfs_remove_dir(), while the item is still guaranteed to be there. A reference obtained just before that stays harmless, as create_link() rechecks CONFIGFS_USET_DROPPING, already set by configfs_detach_prep(). Both configfs_unregister_subsystem() paths d_drop() after detaching, so this only makes rmdir match them. Reported-by: syzbot+6b16e3d085833cbf3e25@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6b16e3d085833cbf3e25 Fixes: 7063fbf22611 ("[PATCH] configfs: User-driven configuration filesystem") Cc: stable@vger.kernel.org Signed-off-by: Vasileios Almpanis <vasilisalmpanis@gmail.com> Tested-by: Breno Leitao <leitao@debian.org> Reviewed-by: Breno Leitao <leitao@debian.org> Link: https://patch.msgid.link/20260730093435.195441-3-vasilisalmpanis@gmail.com Signed-off-by: Breno Leitao <leitao@debian.org> Conflicts: fs/configfs/dir.c [1387aedb391a ("configfs: mark pinned dentries persistent") not merged.] Signed-off-by: Ran Hongyun <ranhongyun1@huawei.com> --- fs/configfs/dir.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c index 46540846d815..e7ca50f11996 100644 --- a/fs/configfs/dir.c +++ b/fs/configfs/dir.c @@ -395,8 +395,17 @@ static void remove_dir(struct dentry * d) configfs_remove_dirent(d); - if (d_really_is_positive(d)) - simple_rmdir(d_inode(parent),d); + if (d_really_is_positive(d)) { + if (!simple_rmdir(d_inode(parent), d)) + /* + * configfs_get_config_item() takes a hashed dentry as + * proof that ->s_element is still alive. Our caller + * is about to drop the last reference to the item and + * the VFS will not unhash until after we return, so + * unhash it here. + */ + d_drop(d); + } pr_debug(" o %pd removing done (%d)\n", d, d_count(d)); -- 2.52.0