block: Don't allow an atomic write be truncated in blkdev_write_iter()

[ Upstream commit 2cbd51f1f8739fd2fdf4bae1386bcf75ce0176ba ]

A write which goes past the end of the bdev in blkdev_write_iter() will
be truncated. Truncating cannot tolerated for an atomic write, so error
that condition.

Fixes: caf336f81b3a ("block: Add fops atomic write support")
Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20241127092318.632790-1-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/block/fops.c b/block/fops.c
index 56db751bba49b829d189cf8512bf0017bc24ffc2..16bb5ae7023798aa51cca9444e081def51f3038a 100644 (file)
--- a/block/fops.c
+++ b/block/fops.c
@@ -676,6 +676,7 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
        struct file *file = iocb->ki_filp;
        struct inode *bd_inode = bdev_file_inode(file);
        struct block_device *bdev = I_BDEV(bd_inode);
+       bool atomic = iocb->ki_flags & IOCB_ATOMIC;
        loff_t size = bdev_nr_bytes(bdev);
        size_t shorted = 0;
        ssize_t ret;
@@ -695,7 +696,7 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
        if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
                return -EOPNOTSUPP;
 
-       if (iocb->ki_flags & IOCB_ATOMIC) {
+       if (atomic) {
                ret = generic_atomic_write_valid(iocb, from);
                if (ret)
                        return ret;
@@ -703,6 +704,8 @@ static ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
        size -= iocb->ki_pos;
        if (iov_iter_count(from) > size) {
+               if (atomic)
+                       return -EINVAL;
                shorted = iov_iter_count(from) - size;
                iov_iter_truncate(from, size);
        }