Discarding blocks and buffers under a mounted filesystem is hardly anything admin wants to do. Usually it will confuse the filesystem and sometimes the loss of buffer_head state (including b_private field) can even cause crashes like: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 PGD 0 P4D 0 Oops: 0002 [#1] SMP PTI CPU: 4 PID: 203778 Comm: jbd2/dm-3-8 Kdump: loaded Tainted: G O --------- - - 4.18.0-147.5.0.5.h126.eulerosv2r9.x86_64 #1 Hardware name: Huawei RH2288H V3/BC11HGSA0, BIOS 1.57 08/11/2015 RIP: 0010:jbd2_journal_grab_journal_head+0x1b/0x40 [jbd2] ... Call Trace: __jbd2_journal_insert_checkpoint+0x23/0x70 [jbd2] jbd2_journal_commit_transaction+0x155f/0x1b60 [jbd2] kjournald2+0xbd/0x270 [jbd2] So refuse fallocate(2) and BLKZEROOUT, BLKDISCARD, BLKSECDISCARD ioctls for a block device having filesystem mounted. Reported-by: Ye Bin <yebin10@xxxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> --- block/ioctl.c | 19 ++++++++++++++++++- fs/block_dev.c | 9 +++++++++ 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/block/ioctl.c b/block/ioctl.c index bdb3bbb253d9..0e3a46b0ffc8 100644 --- a/block/ioctl.c +++ b/block/ioctl.c @@ -113,7 +113,7 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode, uint64_t start, len; struct request_queue *q = bdev_get_queue(bdev); struct address_space *mapping = bdev->bd_inode->i_mapping; - + struct super_block *sb; if (!(mode & FMODE_WRITE)) return -EBADF; @@ -134,6 +134,14 @@ static int blk_ioctl_discard(struct block_device *bdev, fmode_t mode, if (start + len > i_size_read(bdev->bd_inode)) return -EINVAL; + /* + * Don't mess with device with mounted filesystem. + */ + sb = get_super(bdev); + if (sb) { + drop_super(sb); + return -EBUSY; + } truncate_inode_pages_range(mapping, start, start + len - 1); return blkdev_issue_discard(bdev, start >> 9, len >> 9, GFP_KERNEL, flags); @@ -145,6 +153,7 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode, uint64_t range[2]; struct address_space *mapping; uint64_t start, end, len; + struct super_block *sb; if (!(mode & FMODE_WRITE)) return -EBADF; @@ -165,6 +174,14 @@ static int blk_ioctl_zeroout(struct block_device *bdev, fmode_t mode, if (end < start) return -EINVAL; + /* + * Don't mess with device with mounted filesystem. + */ + sb = get_super(bdev); + if (sb) { + drop_super(sb); + return -EBUSY; + } /* Invalidate the page cache, including dirty pages */ mapping = bdev->bd_inode->i_mapping; truncate_inode_pages_range(mapping, start, end); diff --git a/fs/block_dev.c b/fs/block_dev.c index 8ae833e00443..5b398eb7c34c 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1973,6 +1973,7 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start, loff_t end = start + len - 1; loff_t isize; int error; + struct super_block *sb; /* Fail if we don't recognize the flags. */ if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED) @@ -1996,6 +1997,14 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start, if ((start | len) & (bdev_logical_block_size(bdev) - 1)) return -EINVAL; + /* + * Don't mess with device with mounted filesystem. + */ + sb = get_super(bdev); + if (sb) { + drop_super(sb); + return -EBUSY; + } /* Invalidate the page cache, including dirty pages. */ mapping = bdev->bd_inode->i_mapping; truncate_inode_pages_range(mapping, start, end); -- 2.16.4