The motivation for this is to remove the SOL_SOCKET limitation from io_uring_cmd_getsockopt().
The reason for this limitation is that io_uring_cmd_getsockopt() passes a kernel pointer. The first idea would be to change the optval and optlen arguments to the protocol specific hooks also to sockptr_t, as that is already used for setsockopt() and also by do_sock_getsockopt() sk_getsockopt() and BPF_CGROUP_RUN_PROG_GETSOCKOPT(). But as Linus don't like 'sockptr_t' I used a different approach. Instead of passing the optlen as user or kernel pointer, we only ever pass a kernel pointer and do the translation from/to userspace in do_sock_getsockopt(). The simple solution would be to just remove the '__user' from the int *optlen argument, but it seems the compiler doesn't complain about '__user' vs. without it, so instead I used a helper struct in order to make sure everything compiles with a typesafe change. That together with get_optlen() and put_optlen() helper macros make it relatively easy to review and check the behaviour is most likely unchanged. In order to avoid uapi changes regarding different error code orders regarding -EFAULT, the real -EFAULT handling is deferred to get_optlen() and put_optlen(). This allows io_uring_cmd_getsockopt() to remove the SOL_SOCKET limitation. Removing 'sockptr_t optlen' from existing code is for patch for another day. Link: https://lore.kernel.org/io-uring/[email protected]/T/#t Cc: Jens Axboe <[email protected]> Cc: Pavel Begunkov <[email protected]> Cc: Breno Leitao <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Jakub Kicinski <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Karsten Keil <[email protected]> Cc: Ayush Sawal <[email protected]> Cc: Andrew Lunn <[email protected]> Cc: "David S. Miller" <[email protected]> Cc: Eric Dumazet <[email protected]> Cc: Paolo Abeni <[email protected]> Cc: Simon Horman <[email protected]> Cc: Kuniyuki Iwashima <[email protected]> Cc: Willem de Bruijn <[email protected]> Cc: David Ahern <[email protected]> Cc: Marcelo Ricardo Leitner <[email protected]> Cc: Xin Long <[email protected]> Cc: Neal Cardwell <[email protected]> Cc: Joerg Reuter <[email protected]> Cc: Marcel Holtmann <[email protected]> Cc: Johan Hedberg <[email protected]> Cc: Luiz Augusto von Dentz <[email protected]> Cc: Oliver Hartkopp <[email protected]> Cc: Marc Kleine-Budde <[email protected]> Cc: Robin van der Gracht <[email protected]> Cc: Oleksij Rempel <[email protected]> Cc: [email protected] Cc: Alexander Aring <[email protected]> Cc: Stefan Schmidt <[email protected]> Cc: Miquel Raynal <[email protected]> Cc: Alexandra Winter <[email protected]> Cc: Thorsten Winkler <[email protected]> Cc: James Chapman <[email protected]> Cc: Jeremy Kerr <[email protected]> Cc: Matt Johnston <[email protected]> Cc: Matthieu Baerts <[email protected]> Cc: Mat Martineau <[email protected]> Cc: Geliang Tang <[email protected]> Cc: Krzysztof Kozlowski <[email protected]> Cc: Remi Denis-Courmont <[email protected]> Cc: Allison Henderson <[email protected]> Cc: David Howells <[email protected]> Cc: Marc Dionne <[email protected]> Cc: Wenjia Zhang <[email protected]> Cc: Jan Karcher <[email protected]> Cc: "D. Wythe" <[email protected]> Cc: Tony Lu <[email protected]> Cc: Wen Gu <[email protected]> Cc: Jon Maloy <[email protected]> Cc: Boris Pismenny <[email protected]> Cc: John Fastabend <[email protected]> Cc: Stefano Garzarella <[email protected]> Cc: Martin Schiller <[email protected]> Cc: "Björn Töpel" <[email protected]> Cc: Magnus Karlsson <[email protected]> Cc: Maciej Fijalkowski <[email protected]> Cc: Jonathan Lemon <[email protected]> Cc: Alexei Starovoitov <[email protected]> Cc: Daniel Borkmann <[email protected]> Cc: Jesper Dangaard Brouer <[email protected]> CC: Stefan Metzmacher <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Signed-off-by: Stefan Metzmacher <[email protected]> --- include/linux/sockptr.h | 20 +++++++++++++++----- net/socket.c | 31 +++++++++++++++++++++++++++++-- 2 files changed, 44 insertions(+), 7 deletions(-) diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h index 1baf66f26f4f..06ec7fd73028 100644 --- a/include/linux/sockptr.h +++ b/include/linux/sockptr.h @@ -170,20 +170,25 @@ static inline int check_zeroed_sockptr(sockptr_t src, size_t offset, } typedef struct { - int __user *up; + int *kp; } optlen_t; #define __check_optlen_t(__optlen) \ ({ \ optlen_t *__ptr __maybe_unused = &__optlen; \ - BUILD_BUG_ON(sizeof(*((__ptr)->up)) != sizeof(int)); \ + BUILD_BUG_ON(sizeof(*((__ptr)->kp)) != sizeof(int)); \ }) #define get_optlen(__val, __optlen) \ ({ \ long __err; \ __check_optlen_t(__optlen); \ - __err = get_user(__val, __optlen.up); \ + if ((__optlen).kp != NULL) { \ + (__val) = *((__optlen).kp); \ + __err = 0; \ + } else { \ + __err = -EFAULT; \ + } \ __err; \ }) @@ -191,13 +196,18 @@ typedef struct { ({ \ long __err; \ __check_optlen_t(__optlen); \ - __err = put_user(__val, __optlen.up); \ + if ((__optlen).kp != NULL) { \ + *((__optlen).kp) = (__val); \ + __err = 0; \ + } else { \ + __err = -EFAULT; \ + } \ __err; \ }) static inline sockptr_t OPTLEN_SOCKPTR(optlen_t optlen) { - return (sockptr_t) { .user = optlen.up, }; + return (sockptr_t) { .kernel = optlen.kp, .is_kernel = true }; } #endif /* _LINUX_SOCKPTR_H */ diff --git a/net/socket.c b/net/socket.c index fa2de12c10e6..81e5c9767bbc 100644 --- a/net/socket.c +++ b/net/socket.c @@ -2350,15 +2350,42 @@ int do_sock_getsockopt(struct socket *sock, bool compat, int level, } else if (unlikely(!ops->getsockopt)) { err = -EOPNOTSUPP; } else { - optlen_t _optlen = { .up = NULL, }; + optlen_t _optlen = { .kp = NULL, }; + int koptlen; if (WARN_ONCE(optval.is_kernel, "Invalid argument type")) return -EOPNOTSUPP; - _optlen.up = optlen.user; + if (optlen.is_kernel) { + _optlen.kp = optlen.kernel; + } else if (optlen.user != NULL) { + /* + * If optlen.user is NULL, + * we pass _optlen.kp = NULL + * in order to avoid breaking + * any uapi for getsockopt() + * implementations that ignore + * the optlen pointer completely + * or do any level and optname + * checking before hitting a + * potential -EFAULT condition. + * + * Also when optlen.user is not NULL, + * but copy_from_sockptr() causes -EFAULT, + * we'll pass optlen.kp = NULL in order + * to defer a possible -EFAULT return + * to the caller to get_optlen() and put_optlen(). + */ + if (copy_from_sockptr(&koptlen, optlen, sizeof(koptlen)) == 0) + _optlen.kp = &koptlen; + } err = ops->getsockopt(sock, level, optname, optval.user, _optlen); + if (err != -EFAULT && _optlen.kp == &koptlen) { + if (copy_to_sockptr(optlen, &koptlen, sizeof(koptlen))) + return -EFAULT; + } } if (!compat) -- 2.34.1
