From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 42FEB1A3A95; Sun, 24 Nov 2024 12:39:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732451980; cv=none; b=L5al5CT0DA2bl2flfQ7XLA9bsoV37Cw/2zbGZ91IP79FMnjnsKPyzq5yM6xpjr4Y0YIwMrNTYCI8bzd9w9mcdKjhCeRPDPODMtRgrtnF6XHKRBllCVYITlUQv3bjpM/Rz24jMlTa73HJ950DYY94WLxYQavADSjKobI/U3hDd7w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732451980; c=relaxed/simple; bh=TIZKjhwHK7qmPxSJrt3PxIUO5pcAYHIY+FvdT3wtjn0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Q+BRgbmqHwKCP4htoR6CQjaiYaZ8Zt30Q9ttbj++Vm+eQQfYVABRyYtBvY6Nb7QlyPH5KObTMvVeuP583vL0FPtk4rtgzI2IccQDlgQN7Ytz9tTXtxwHOOV7HVD5OzEnJA9rBVF1BuzH7G8GrYpIw/YmLfCjWcQta/u0Z2dDPlc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=j0JtRVau; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="j0JtRVau" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C29EC4CED1; Sun, 24 Nov 2024 12:39:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732451979; bh=TIZKjhwHK7qmPxSJrt3PxIUO5pcAYHIY+FvdT3wtjn0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=j0JtRVauoLbLoHxG2KQ2CiiXH0imzqnLT5IRwTPTWGMWVr0dYkVY8pq8ANU2cOXWU MTo0NkX3l1yivbzSUKChrWt92Rqvfyux/iQs8TSe8sWJ6DBx/4duFsu9anRWDlPM8I IeElKcbPxPZju9AMtJvSuwv/OAOj2YT4WEyf0SAWTVhMED8KUh9R5LNuD0p4W3HGMb w7yATbYiuEN6KlpFkjTxjXhrv3jHNEIGe169dVe+rO4LZ/jwlIKhSVxdcz8gCAhn2q yhBpArwkyj0o7qRDfgAJ22hu1vC6j0E9gUrZgOMWQla1zIarJvo5VN3o6iWaGE0Cje gFzS2eYUgJObA== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Qu Wenruo , Filipe Manana , Fabian Vogt , David Sterba , Sasha Levin , clm@fb.com, josef@toxicpanda.com, linux-btrfs@vger.kernel.org Subject: [PATCH AUTOSEL 6.12 12/19] btrfs: canonicalize the device path before adding it Date: Sun, 24 Nov 2024 07:38:47 -0500 Message-ID: <20241124123912.3335344-12-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241124123912.3335344-1-sashal@kernel.org> References: <20241124123912.3335344-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.12.1 Content-Transfer-Encoding: 8bit From: Qu Wenruo [ Upstream commit 7e06de7c83a746e58d4701e013182af133395188 ] [PROBLEM] Currently btrfs accepts any file path for its device, resulting some weird situation: # ./mount_by_fd /dev/test/scratch1 /mnt/btrfs/ The program has the following source code: #include #include #include int main(int argc, char *argv[]) { int fd = open(argv[1], O_RDWR); char path[256]; snprintf(path, sizeof(path), "/proc/self/fd/%d", fd); return mount(path, argv[2], "btrfs", 0, NULL); } Then we can have the following weird device path: BTRFS: device fsid 2378be81-fe12-46d2-a9e8-68cf08dd98d5 devid 1 transid 7 /proc/self/fd/3 (253:2) scanned by mount_by_fd (18440) Normally it's not a big deal, and later udev can trigger a device path rename. But if udev didn't trigger, the device path "/proc/self/fd/3" will show up in mtab. [CAUSE] For filename "/proc/self/fd/3", it means the opened file descriptor 3. In above case, it's exactly the device we want to open, aka points to "/dev/test/scratch1" which is another symlink pointing to "/dev/dm-2". Inside kernel we solve the mount source using LOOKUP_FOLLOW, which follows the symbolic link and grab the proper block device. But inside btrfs we also save the filename into btrfs_device::name, and utilize that member to report our mount source, which leads to the above situation. [FIX] Instead of unconditionally trust the path, check if the original file (not following the symbolic link) is inside "/dev/", if not, then manually lookup the path to its final destination, and use that as our device path. This allows us to still use symbolic links, like "/dev/mapper/test-scratch" from LVM2, which is required for fstests runs with LVM2 setup. And for really weird names, like the above case, we solve it to "/dev/dm-2" instead. Reviewed-by: Filipe Manana Link: https://bugzilla.suse.com/show_bug.cgi?id=1230641 Reported-by: Fabian Vogt Signed-off-by: Qu Wenruo Signed-off-by: David Sterba Signed-off-by: Sasha Levin --- fs/btrfs/volumes.c | 87 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 86 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 5e75a4e3a5be5..5895397364aac 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -732,6 +732,78 @@ const u8 *btrfs_sb_fsid_ptr(const struct btrfs_super_block *sb) return has_metadata_uuid ? sb->metadata_uuid : sb->fsid; } +/* + * We can have very weird soft links passed in. + * One example is "/proc/self/fd/", which can be a soft link to + * a block device. + * + * But it's never a good idea to use those weird names. + * Here we check if the path (not following symlinks) is a good one inside + * "/dev/". + */ +static bool is_good_dev_path(const char *dev_path) +{ + struct path path = { .mnt = NULL, .dentry = NULL }; + char *path_buf = NULL; + char *resolved_path; + bool is_good = false; + int ret; + + if (!dev_path) + goto out; + + path_buf = kmalloc(PATH_MAX, GFP_KERNEL); + if (!path_buf) + goto out; + + /* + * Do not follow soft link, just check if the original path is inside + * "/dev/". + */ + ret = kern_path(dev_path, 0, &path); + if (ret) + goto out; + resolved_path = d_path(&path, path_buf, PATH_MAX); + if (IS_ERR(resolved_path)) + goto out; + if (strncmp(resolved_path, "/dev/", strlen("/dev/"))) + goto out; + is_good = true; +out: + kfree(path_buf); + path_put(&path); + return is_good; +} + +static int get_canonical_dev_path(const char *dev_path, char *canonical) +{ + struct path path = { .mnt = NULL, .dentry = NULL }; + char *path_buf = NULL; + char *resolved_path; + int ret; + + if (!dev_path) { + ret = -EINVAL; + goto out; + } + + path_buf = kmalloc(PATH_MAX, GFP_KERNEL); + if (!path_buf) { + ret = -ENOMEM; + goto out; + } + + ret = kern_path(dev_path, LOOKUP_FOLLOW, &path); + if (ret) + goto out; + resolved_path = d_path(&path, path_buf, PATH_MAX); + ret = strscpy(canonical, resolved_path, PATH_MAX); +out: + kfree(path_buf); + path_put(&path); + return ret; +} + static bool is_same_device(struct btrfs_device *device, const char *new_path) { struct path old = { .mnt = NULL, .dentry = NULL }; @@ -1419,12 +1491,23 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags, bool new_device_added = false; struct btrfs_device *device = NULL; struct file *bdev_file; + char *canonical_path = NULL; u64 bytenr; dev_t devt; int ret; lockdep_assert_held(&uuid_mutex); + if (!is_good_dev_path(path)) { + canonical_path = kmalloc(PATH_MAX, GFP_KERNEL); + if (canonical_path) { + ret = get_canonical_dev_path(path, canonical_path); + if (ret < 0) { + kfree(canonical_path); + canonical_path = NULL; + } + } + } /* * Avoid an exclusive open here, as the systemd-udev may initiate the * device scan which may race with the user's mount or mkfs command, @@ -1469,7 +1552,8 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags, goto free_disk_super; } - device = device_list_add(path, disk_super, &new_device_added); + device = device_list_add(canonical_path ? : path, disk_super, + &new_device_added); if (!IS_ERR(device) && new_device_added) btrfs_free_stale_devices(device->devt, device); @@ -1478,6 +1562,7 @@ struct btrfs_device *btrfs_scan_one_device(const char *path, blk_mode_t flags, error_bdev_put: fput(bdev_file); + kfree(canonical_path); return device; } -- 2.43.0