Patch "block: Don't allow an atomic write be truncated in blkdev_write_iter()" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-don-t-allow-an-atomic-write-be-truncated-in-bl.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c007d76ea01fd93692d13ceaa2a62ff3049f8dfb
Author: John Garry <john.g.garry@xxxxxxxxxx>
Date:   Wed Nov 27 09:23:18 2024 +0000

    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@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Link: https://lore.kernel.org/r/20241127092318.632790-1-john.g.garry@xxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/fops.c b/block/fops.c
index 2d01c90076813..13a67940d0408 100644
--- 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);
 	}