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net: Block MSG_SENDPAGE_* from being passed to sendmsg() by userspace

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It is necessary to allow MSG_SENDPAGE_* to be passed into ->sendmsg() to
allow sendmsg(MSG_SPLICE_PAGES) to replace ->sendpage().  Unblocking them
in the network protocol, however, allows these flags to be passed in by
userspace too[1].

Fix this by marking MSG_SENDPAGE_NOPOLICY, MSG_SENDPAGE_NOTLAST and
MSG_SENDPAGE_DECRYPTED as internal flags, which causes sendmsg() to object
if they are passed to sendmsg() by userspace.  Network protocol ->sendmsg()
implementations can then allow them through.

Note that it should be possible to remove MSG_SENDPAGE_NOTLAST once
sendpage is removed as a whole slew of pages will be passed in in one go by
splice through sendmsg, with MSG_MORE being set if it has more data waiting
in the pipe.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: Boris Pismenny <borisp@nvidia.com>
cc: John Fastabend <john.fastabend@gmail.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/r/20230526181338.03a99016@kernel.org/ [1]
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2023-06-07 19:19:07 +01:00 committed by Jakub Kicinski
parent 736013292e
commit 4fe38acdac
1 changed files with 3 additions and 1 deletions
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4
include/linux/socket.h
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@ -339,7 +339,9 @@ struct ucred {
#endif
/* Flags to be cleared on entry by sendmsg and sendmmsg syscalls */
#define MSG_INTERNAL_SENDMSG_FLAGS (MSG_SPLICE_PAGES)
#define MSG_INTERNAL_SENDMSG_FLAGS \
(MSG_SPLICE_PAGES | MSG_SENDPAGE_NOPOLICY | MSG_SENDPAGE_NOTLAST | \
MSG_SENDPAGE_DECRYPTED)
/* Setsockoptions(2) level. Thanks to BSD these must match IPPROTO_xxx */
#define SOL_IP 0