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Fri, 19 Jan 2024 18:47:55 +0000 (UTC) Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 92474136F5; Fri, 19 Jan 2024 18:47:54 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id YGWeEdrDqmU8DAAAD6G6ig (envelope-from ); Fri, 19 Jan 2024 18:47:54 +0000 From: Gabriel Krisman Bertazi To: viro@zeniv.linux.org.uk, ebiggers@kernel.org, jaegeuk@kernel.org, tytso@mit.edu Cc: linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, amir73il@gmail.com, Gabriel Krisman Bertazi Subject: [PATCH v3 01/10] ovl: Reject mounting case-insensitive filesystems Date: Fri, 19 Jan 2024 15:47:33 -0300 Message-ID: <20240119184742.31088-2-krisman@suse.de> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240119184742.31088-1-krisman@suse.de> References: <20240119184742.31088-1-krisman@suse.de> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Spam-Level: Authentication-Results: smtp-out2.suse.de; none X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[] X-Spam-Score: -4.00 X-Rspamd-Queue-Id: 11E241F809 X-Spam-Flag: NO overlayfs relies on the filesystem setting DCACHE_OP_HASH or DCACHE_OP_COMPARE to reject mounting over case-insensitive directories. Since commit bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops"), we set ->d_op through a hook in ->d_lookup, which means the root dentry won't have them, causing the mount to accidentally succeed. In v6.7-rc7, the following sequence will succeed to mount, but any dentry other than the root dentry will be a "weird" dentry to ovl and fail with EREMOTE. mkfs.ext4 -O casefold lower.img mount -O loop lower.img lower mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=work ovl /mnt Mounting on a subdirectory fails, as expected, because DCACHE_OP_HASH and DCACHE_OP_COMPARE are properly set by ->lookup. Fix by explicitly rejecting superblocks that allow case-insensitive dentries. While there, re-sort the entries to have more descriptive error messages first. Fixes: bb9cd9106b22 ("fscrypt: Have filesystems handle their d_ops") Signed-off-by: Gabriel Krisman Bertazi Acked-by: Amir Goldstein --- changes since v2: - Re-sort checks to trigger more descriptive error messages first (Amir) - Add code comment (Amir) --- fs/overlayfs/params.c | 13 ++++++++++--- include/linux/fs.h | 9 +++++++++ 2 files changed, 19 insertions(+), 3 deletions(-) diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c index 3fe2dde1598f..09a4973f26f9 100644 --- a/fs/overlayfs/params.c +++ b/fs/overlayfs/params.c @@ -280,12 +280,19 @@ static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path, { struct ovl_fs_context *ctx = fc->fs_private; - if (ovl_dentry_weird(path->dentry)) - return invalfc(fc, "filesystem on %s not supported", name); - if (!d_is_dir(path->dentry)) return invalfc(fc, "%s is not a directory", name); + /* + * Root dentries of case-insensitive filesystems might not have + * the dentry operations set, but still be incompatible with + * overlayfs. Check explicitly to prevent post-mount failures. + */ + if (sb_has_encoding(path->mnt->mnt_sb)) + return invalfc(fc, "case-insensitive filesystem on %s not supported", name); + + if (ovl_dentry_weird(path->dentry)) + return invalfc(fc, "filesystem on %s not supported", name); /* * Check whether upper path is read-only here to report failures diff --git a/include/linux/fs.h b/include/linux/fs.h index 98b7a7a8c42e..e6667ece5e64 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3203,6 +3203,15 @@ extern int generic_check_addressable(unsigned, u64); extern void generic_set_encrypted_ci_d_ops(struct dentry *dentry); +static inline bool sb_has_encoding(const struct super_block *sb) +{ +#if IS_ENABLED(CONFIG_UNICODE) + return !!sb->s_encoding; +#else + return false; +#endif +} + int may_setattr(struct mnt_idmap *idmap, struct inode *inode, unsigned int ia_valid); int setattr_prepare(struct mnt_idmap *, struct dentry *, struct iattr *);