[PATCH v2 1/3] fuse: check if copy_file_range() returns larger than requested size

[PATCH v2 1/3] fuse: check if copy_file_range() returns larger than requested size

[Miklos Szeredi]

Just like write(), copy_file_range() should check if the return value is
less or equal to the requested number of bytes.

Reported-by: Chunsheng Luo <luochunsheng@ustc.edu>
Closes: https://lore.kernel.org/all/20250807062425.694-1-luochunsheng@ustc.edu/
Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()")
Cc: <stable@vger.kernel.org> # v4.20
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/fuse/file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 5525a4520b0f..45207a6bb85f 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -3026,6 +3026,9 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
 		fc->no_copy_file_range = 1;
 		err = -EOPNOTSUPP;
 	}
+	if (!err && outarg.size > len)
+		err = -EIO;
+
 	if (err)
 		goto out;
 
-- 
2.49.0

[PATCH v2 2/3] fuse: prevent overflow in copy_file_range return value

[Miklos Szeredi]

The FUSE protocol uses struct fuse_write_out to convey the return value of
copy_file_range, which is restricted to uint32_t.  But the COPY_FILE_RANGE
interface supports a 64-bit size copies.

Currently the number of bytes copied is silently truncated to 32-bit, which
may result in poor performance or even failure to copy in case of
truncation to zero.

Reported-by: Florian Weimer <fweimer@redhat.com>
Closes: https://lore.kernel.org/all/lhuh5ynl8z5.fsf@oldenburg.str.redhat.com/
Fixes: 88bc7d5097a1 ("fuse: add support for copy_file_range()")
Cc: <stable@vger.kernel.org> # v4.20
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/fuse/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 45207a6bb85f..4adcf09d4b01 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2960,7 +2960,7 @@ static ssize_t __fuse_copy_file_range(struct file *file_in, loff_t pos_in,
 		.nodeid_out = ff_out->nodeid,
 		.fh_out = ff_out->fh,
 		.off_out = pos_out,
-		.len = len,
+		.len = min_t(size_t, len, UINT_MAX & PAGE_MASK),
 		.flags = flags
 	};
 	struct fuse_write_out outarg;
-- 
2.49.0