| Message ID | 1428985.1686737388@warthog.procyon.org.uk (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | ca2d49f77ce4531c74ba207b1e07b55f5ced5ab4 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] splice, net: Fix splice_to_socket() to handle pipe bufs larger than a page | expand |
Hello: This patch was applied to netdev/net-next.git (main) by Jakub Kicinski <kuba@kernel.org>: On Wed, 14 Jun 2023 11:09:48 +0100 you wrote: > splice_to_socket() assumes that a pipe_buffer won't hold more than a single > page of data - but this assumption can be violated by skb_splice_bits() > when it splices from a socket into a pipe. > > The problem is that splice_to_socket() doesn't advance the pipe_buffer > length and offset when transcribing from the pipe buf into a bio_vec, so if > the buf is >PAGE_SIZE, it keeps repeating the same initial chunk and > doesn't advance the tail index. It then subtracts this from "remain" and > overcounts the amount of data to be sent. > > [...] Here is the summary with links: - [net-next] splice, net: Fix splice_to_socket() to handle pipe bufs larger than a page https://git.kernel.org/netdev/net-next/c/ca2d49f77ce4 You are awesome, thank you!
diff --git a/fs/splice.c b/fs/splice.c index e337630aed64..567a1f03ea1e 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -886,7 +886,6 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out, } seg = min_t(size_t, remain, buf->len); - seg = min_t(size_t, seg, PAGE_SIZE); ret = pipe_buf_confirm(pipe, buf); if (unlikely(ret)) { @@ -897,10 +896,9 @@ ssize_t splice_to_socket(struct pipe_inode_info *pipe, struct file *out, bvec_set_page(&bvec[bc++], buf->page, seg, buf->offset); remain -= seg; - if (seg >= buf->len) - tail++; - if (bc >= ARRAY_SIZE(bvec)) + if (remain == 0 || bc >= ARRAY_SIZE(bvec)) break; + tail++; } if (!bc)
splice_to_socket() assumes that a pipe_buffer won't hold more than a single page of data - but this assumption can be violated by skb_splice_bits() when it splices from a socket into a pipe. The problem is that splice_to_socket() doesn't advance the pipe_buffer length and offset when transcribing from the pipe buf into a bio_vec, so if the buf is >PAGE_SIZE, it keeps repeating the same initial chunk and doesn't advance the tail index. It then subtracts this from "remain" and overcounts the amount of data to be sent. The cleanup phase then tries to overclean the pipe, hits an unused pipe buf and a NULL-pointer dereference occurs. Fix this by not restricting the bio_vec size to PAGE_SIZE and instead transcribing the entirety of each pipe_buffer into a single bio_vec and advancing the tail index if remain hasn't hit zero yet. Large bio_vecs will then be split up by iterator functions such as iov_iter_extract_pages(). This resulted in a KASAN report looking like: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] ... RIP: 0010:pipe_buf_release include/linux/pipe_fs_i.h:203 [inline] RIP: 0010:splice_to_socket+0xa91/0xe30 fs/splice.c:933 Fixes: 2dc334f1a63a ("splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()") Reported-by: syzbot+f9e28a23426ac3b24f20@syzkaller.appspotmail.com Link: https://lore.kernel.org/r/0000000000000900e905fdeb8e39@google.com/ Tested-by: syzbot+f9e28a23426ac3b24f20@syzkaller.appspotmail.com Signed-off-by: David Howells <dhowells@redhat.com> cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com> cc: David Ahern <dsahern@kernel.org> cc: "David S. Miller" <davem@davemloft.net> cc: Eric Dumazet <edumazet@google.com> cc: Jakub Kicinski <kuba@kernel.org> cc: Paolo Abeni <pabeni@redhat.com> cc: Jens Axboe <axboe@kernel.dk> cc: Matthew Wilcox <willy@infradead.org> cc: Christian Brauner <brauner@kernel.org> cc: Alexander Viro <viro@zeniv.linux.org.uk> cc: netdev@vger.kernel.org cc: linux-fsdevel@vger.kernel.org --- fs/splice.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)