In mount operations, cgroup device access permissions are checked only when a new super_block is created. If the device has already been mounted, no permission check is performed since the super_block already exists. As a result, a process belonging to a cgroup without access permissions to the device can still perform a mount operation successfully.
To reproduce: # mount /dev/loop0 /mnt/test0 # echo $$ > /sys/fs/cgroup/machine.slice/CTID/cgroup.procs # mount /dev/loop0 /mnt/test1 # If the device was not mounted before, the mount operation fails as expected: # echo $$ > /sys/fs/cgroup/machine.slice/CTID/cgroup.procs # mount /dev/loop0 /mnt/test1 mount: /mnt/test1: permission denied. This patch adds a cgroup permission check for the mounting process before obtaining the device's super_block. As a result, even if the device has already been mounted and the super_block exists, the mount operation will be denied when the process lacks the appropriate cgroup permissions. v2: removed redundant cgroup permission check when creating a new superblock in setup_dbev_super. v3: no changes v4: revert v2 https://virtuozzo.atlassian.net/browse/VSTOR-105978 Signed-off-by: Aleksei Oladko <[email protected]> --- block/blk.h | 1 - fs/super.c | 14 +++++++++++++- include/linux/blkdev.h | 1 + include/linux/fs.h | 1 + 4 files changed, 15 insertions(+), 2 deletions(-) diff --git a/block/blk.h b/block/blk.h index c718e4291db0..8610d87e5050 100644 --- a/block/blk.h +++ b/block/blk.h @@ -727,7 +727,6 @@ static inline void bio_issue_init(struct bio_issue *issue, void bdev_release(struct file *bdev_file); int bdev_open(struct block_device *bdev, blk_mode_t mode, void *holder, const struct blk_holder_ops *hops, struct file *bdev_file); -int bdev_permission(dev_t dev, blk_mode_t mode, void *holder); void blk_integrity_generate(struct bio *bio); void blk_integrity_verify(struct bio *bio); diff --git a/fs/super.c b/fs/super.c index faf37790544e..6a2a88f07c12 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1407,6 +1407,18 @@ struct super_block *sget_dev(struct fs_context *fc, dev_t dev) } EXPORT_SYMBOL(sget_dev); +struct super_block *sget_dev_check(struct fs_context *fc, dev_t dev) +{ + int ret; + + blk_mode_t mode = sb_open_mode(fc->sb_flags) | BLK_OPEN_MOUNT; + ret = bdev_permission(dev, mode, fc); + if (ret) + return ERR_PTR(ret); + return sget_dev(fc, dev); +} +EXPORT_SYMBOL(sget_dev_check); + #ifdef CONFIG_BLOCK /* * Lock the superblock that is holder of the bdev. Returns the superblock @@ -1664,7 +1676,7 @@ int get_tree_bdev_flags(struct fs_context *fc, return error; } fc->sb_flags |= SB_NOSEC; - s = sget_dev(fc, dev); + s = sget_dev_check(fc, dev); if (IS_ERR(s)) return PTR_ERR(s); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 64c28dbb44b4..4a66f6aa0441 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1666,6 +1666,7 @@ struct file *bdev_file_open_by_path(const char *path, blk_mode_t mode, int bd_prepare_to_claim(struct block_device *bdev, void *holder, const struct blk_holder_ops *hops); void bd_abort_claiming(struct block_device *bdev, void *holder); +int bdev_permission(dev_t dev, blk_mode_t mode, void *holder); /* just for blk-cgroup, don't use elsewhere */ struct block_device *blkdev_get_no_open(dev_t dev); diff --git a/include/linux/fs.h b/include/linux/fs.h index b6f7809cad29..1f535909524c 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2608,6 +2608,7 @@ struct super_block *sget(struct file_system_type *type, int (*set)(struct super_block *,void *), int flags, void *data); struct super_block *sget_dev(struct fs_context *fc, dev_t dev); +struct super_block *sget_dev_check(struct fs_context *fc, dev_t dev); /* Alas, no aliases. Too much hassle with bringing module.h everywhere */ #define fops_get(fops) ({ \ -- 2.43.0 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
