6.12-stable review patch. If anyone has any objections, please let me know.
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From: Qu Wenruo wqu@suse.com
commit 8fb1dcbbcc1ffe6ed7cf3f0f96d2737491dd1fbf upstream.
This reverts commit 7e06de7c83a746e58d4701e013182af133395188.
Commit 7e06de7c83a7 ("btrfs: canonicalize the device path before adding it") tries to make btrfs to use "/dev/mapper/*" name first, then any filename inside "/dev/" as the device path.
This is mostly fine when there is only the root namespace involved, but when multiple namespace are involved, things can easily go wrong for the d_path() usage.
As d_path() returns a file path that is namespace dependent, the resulted string may not make any sense in another namespace.
Furthermore, the "/dev/" prefix checks itself is not reliable, one can still make a valid initramfs without devtmpfs, and fill all needed device nodes manually.
Overall the userspace has all its might to pass whatever device path for mount, and we are not going to win the war trying to cover every corner case.
So just revert that commit, and do no extra d_path() based file path sanity check.
CC: stable@vger.kernel.org # 6.12+ Link: https://lore.kernel.org/linux-fsdevel/20250115185608.GA2223535@zen.localdoma... Reviewed-by: Boris Burkov boris@bur.io Signed-off-by: Qu Wenruo wqu@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/volumes.c | 91 ----------------------------------------------------- 1 file changed, 1 insertion(+), 90 deletions(-)
--- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -732,82 +732,6 @@ const u8 *btrfs_sb_fsid_ptr(const struct return has_metadata_uuid ? sb->metadata_uuid : sb->fsid; }
-/* - * We can have very weird soft links passed in. - * One example is "/proc/self/fd/<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); - if (IS_ERR(resolved_path)) { - ret = PTR_ERR(resolved_path); - goto out; - } - 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 }; @@ -1495,23 +1419,12 @@ struct btrfs_device *btrfs_scan_one_devi 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, @@ -1556,8 +1469,7 @@ struct btrfs_device *btrfs_scan_one_devi goto free_disk_super; }
- device = device_list_add(canonical_path ? : path, disk_super, - &new_device_added); + device = device_list_add(path, disk_super, &new_device_added); if (!IS_ERR(device) && new_device_added) btrfs_free_stale_devices(device->devt, device);
@@ -1566,7 +1478,6 @@ free_disk_super:
error_bdev_put: fput(bdev_file); - kfree(canonical_path);
return device; }