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 v5: * added a cgroup device permission check to mount_bdev * added mandatory cgroup device permission check in sget_dev, introduced _sget_dev without the check https://virtuozzo.atlassian.net/browse/VSTOR-105978 Signed-off-by: Aleksei Oladko <[email protected]> --- block/blk.h | 1 - drivers/mtd/mtdsuper.c | 2 +- fs/super.c | 19 ++++++++++++++++++- include/linux/blkdev.h | 1 + include/linux/fs.h | 1 + 5 files changed, 21 insertions(+), 3 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/drivers/mtd/mtdsuper.c b/drivers/mtd/mtdsuper.c index b7e3763c47f0..417f11bdbf0b 100644 --- a/drivers/mtd/mtdsuper.c +++ b/drivers/mtd/mtdsuper.c @@ -30,7 +30,7 @@ static int mtd_get_sb(struct fs_context *fc, struct super_block *sb; int ret; - sb = sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index)); + sb = _sget_dev(fc, MKDEV(MTD_BLOCK_MAJOR, mtd->index)); if (IS_ERR(sb)) return PTR_ERR(sb); diff --git a/fs/super.c b/fs/super.c index faf37790544e..2c266c869312 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1400,11 +1400,23 @@ static int super_s_dev_test(struct super_block *s, struct fs_context *fc) * Return: an existing or newly created superblock on success, an error * pointer on failure. */ -struct super_block *sget_dev(struct fs_context *fc, dev_t dev) +struct super_block *_sget_dev(struct fs_context *fc, dev_t dev) { fc->sget_key = &dev; return sget_fc(fc, super_s_dev_test, super_s_dev_set); } +EXPORT_SYMBOL(_sget_dev); + +struct super_block *sget_dev(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); #ifdef CONFIG_BLOCK @@ -1722,6 +1734,11 @@ struct dentry *mount_bdev(struct file_system_type *fs_type, if (error) return ERR_PTR(error); + /* Check cgroup permissions before getting super_block */ + error = bdev_permission(dev, sb_open_mode(flags) | BLK_OPEN_MOUNT, data); + if (error) + return ERR_PTR(error); + flags |= SB_NOSEC; s = sget(fs_type, test_bdev_super, set_bdev_super, flags, &dev); if (IS_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..13528ccf09b7 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(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
