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[178.84.201.199]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fee968763sm5328119f8f.56.2026.11.04.10.46.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 10:46:02 -0800 (PST) From: Amir Goldstein To: Greg Kroah-Hartman Cc: Miklos Szeredi , stable@vger.kernel.org, linux-unionfs@vger.kernel.org, Chris Mason , Josef Bacik Subject: [PATCH 6.6 2/2] ovl: use the pinned upper dir in ovl_fix_origin() Date: Wed, 4 Nov 2026 19:45:59 +0100 Message-ID: <20261104184559.3630145-3-amir73il@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261104184559.3630145-1-amir73il@gmail.com> References: <20261104184559.3630145-1-amir73il@gmail.com> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Chris Mason commit 4f61ff2ebfb3d2967b83b6a4d456242244d5a61f upstream. Renames made directly on the upper filesystem during a lookup crash the kernel. A dentry that is passed to vfs_setxattr() must be pinned. ovl_fix_origin() passes upper->d_parent to ovl_set_impure() without a reference, and the lookup holds no lock of the upper directory. A rename on the upper filesystem changes d_parent, and only the child pins the new parent, so a second rename and an rmdir free it. With delays in ovl_fix_origin() and ovl_set_impure(), renaming the upper directory twice and removing the intermediate parent during the lookup of a merge directory without an origin xattr gave a KASAN use-after-free in vfs_setxattr(). Fix this by passing the upper dentry that the overlay parent holds. Fixes: 9678e6303057 ("ovl: fix inconsistent d_ino for legacy merge dir") Cc: stable@vger.kernel.org Signed-off-by: Chris Mason Signed-off-by: Josef Bacik [amir: add helper ovl_set_impure_dir()] Signed-off-by: Amir Goldstein --- [ backport: context: ovl_fix_origin() calls ovl_set_origin() ] fs/overlayfs/namei.c | 6 ++++-- fs/overlayfs/overlayfs.h | 6 ++++++ 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -883,8 +883,10 @@ static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry, return err; err = ovl_set_origin(ofs, lower, upper); - if (!err) - err = ovl_set_impure(dentry->d_parent, upper->d_parent); + if (!err) { + /* upper->d_parent is not stable, use the overlay parent */ + err = ovl_set_impure_dir(dentry->d_parent); + } ovl_drop_write(dentry); return err; diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -492,6 +492,12 @@ int ovl_check_setxattr(struct ovl_fs *ofs, struct dentry *upperdentry, enum ovl_xattr ox, const void *value, size_t size, int xerr); int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry); + +static inline int ovl_set_impure_dir(struct dentry *dentry) +{ + return ovl_set_impure(dentry, ovl_dentry_upper(dentry)); +} + bool ovl_inuse_trylock(struct dentry *dentry); void ovl_inuse_unlock(struct dentry *dentry); bool ovl_is_inuse(struct dentry *dentry); -- backport