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

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>

diff --git a/block/fops.c b/block/fops.c
index 2d01c900768139430301c82d8457a968f022c7e3..13a67940d0408d60130dd66604a5281f5ef06324 100644 (file)
--- a/block/fops.c
+++ b/block/fops.c
@@ -677,6 +677,7 @@ 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;
@@ -696,7 +697,7 @@ 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;
@@ -704,6 +705,8 @@ 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);
        }