From: Jason A. Donenfeld Jason@zx2c4.com
[ Upstream commit 97ef77c52b789ec1411d360ed99dca1efe4b2c81 ]
The original direct splicing mechanism from Jens required the input to be a regular file because it was avoiding the special socket case. It also recognized blkdevs as being close enough to a regular file. But it forgot about chardevs, which behave the same way and work fine here.
This is an okayish heuristic, but it doesn't totally work. For example, a few chardevs should be spliceable here. And a few regular files shouldn't. This patch fixes this by instead checking whether FMODE_LSEEK is set, which represents decently enough what we need rewinding for when splicing to internal pipes.
Fixes: b92ce5589374 ("[PATCH] splice: add direct fd <-> fd splicing support") Cc: Jens Axboe axboe@kernel.dk Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Al Viro viro@zeniv.linux.org.uk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/splice.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/fs/splice.c b/fs/splice.c index e509239d7e06..ae5623244d5e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -895,17 +895,15 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, { struct pipe_inode_info *pipe; long ret, bytes; - umode_t i_mode; size_t len; int i, flags, more;
/* - * We require the input being a regular file, as we don't want to - * randomly drop data for eg socket -> socket splicing. Use the - * piped splicing for that! + * We require the input to be seekable, as we don't want to randomly + * drop data for eg socket -> socket splicing. Use the piped splicing + * for that! */ - i_mode = file_inode(in)->i_mode; - if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode))) + if (unlikely(!(in->f_mode & FMODE_LSEEK))) return -EINVAL;
/*