From 4911de3145a797389577abfdf9a5185d36cc18d7 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Tue, 7 Apr 2026 18:03:13 +0200 Subject: [PATCH 1/5] uaccess: fix ignored_trailing logic in copy_struct_to_user() Currently all callers pass ignored_trailing=NULL, but I have code that will make use of. Now it actually behaves like documented: * If @usize < @ksize, then the kernel is trying to pass userspace a newer struct than it supports. Thus we only copy the interoperable portions (@usize) and ignore the rest (but @ignored_trailing is set to %true if any of the trailing (@ksize - @usize) bytes are non-zero). Fixes: 424a55a4a908 ("uaccess: add copy_struct_to_user helper") Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Dmitry Safonov Cc: Francesco Ruggeri Cc: Salam Noureddine Cc: David Ahern Cc: David S. Miller Cc: Michal Luczaj Cc: David Wei Cc: Luiz Augusto von Dentz Cc: Luiz Augusto von Dentz Cc: Marcel Holtmann Cc: Xin Long Cc: Eric Dumazet Cc: Kuniyuki Iwashima Cc: Paolo Abeni Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Jakub Kicinski Cc: Simon Horman Cc: Aleksa Sarai Cc: Christian Brauner CC: Kees Cook Cc: netdev@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Stefan Metzmacher Link: https://patch.msgid.link/71f69442410c1186ed8ce6d5b4b9d4a5a70edbad.1775576651.git.metze@samba.org Reviewed-by: Aleksa Sarai Signed-off-by: Christian Brauner --- include/linux/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 56328601218c..09a09cc4aac2 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -510,7 +510,7 @@ copy_struct_to_user(void __user *dst, size_t usize, const void *src, return -EFAULT; } if (ignored_trailing) - *ignored_trailing = ksize < usize && + *ignored_trailing = usize < ksize && memchr_inv(src + size, 0, rest) != NULL; /* Copy the interoperable parts of the struct. */ if (copy_to_user(dst, src, size)) From db0493512931fe1e5a71612e6a358df1aa22d80c Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Tue, 7 Apr 2026 18:03:14 +0200 Subject: [PATCH 2/5] sockptr: fix usize check in copy_struct_from_sockptr() for user pointers copy_struct_from_user will never hit the check_zeroed_user() call and will never return -E2BIG if new userspace passed new bits in a larger structure than the current kernel structure. As far as I can there are no critical/related uapi changes in - include/net/bluetooth/bluetooth.h and net/bluetooth/sco.c after the use of copy_struct_from_sockptr in v6.13-rc3 - include/uapi/linux/tcp.h and net/ipv4/tcp_ao.c after the use of copy_struct_from_sockptr in v6.6-rc1 So that new callers will get the correct behavior from the start. Fixes: 4954f17ddefc ("net/tcp: Introduce TCP_AO setsockopt()s") Fixes: ef84703a911f ("net/tcp: Add TCP-AO getsockopt()s") Fixes: faadfaba5e01 ("net/tcp: Add TCP_AO_REPAIR") Fixes: 3e643e4efa1e ("Bluetooth: Improve setsockopt() handling of malformed user input") Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Dmitry Safonov Cc: Francesco Ruggeri Cc: Salam Noureddine Cc: David Ahern Cc: David S. Miller Cc: Michal Luczaj Cc: David Wei Cc: Luiz Augusto von Dentz Cc: Luiz Augusto von Dentz Cc: Marcel Holtmann Cc: Xin Long Cc: Eric Dumazet Cc: Kuniyuki Iwashima Cc: Paolo Abeni Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Jakub Kicinski Cc: Simon Horman Cc: Aleksa Sarai Cc: Christian Brauner CC: Kees Cook Cc: netdev@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Stefan Metzmacher Link: https://patch.msgid.link/cfaedbc33ae9d36adaabf04fa79424f30ff1efdd.1775576651.git.metze@samba.org Reviewed-by: Aleksa Sarai Signed-off-by: Christian Brauner --- include/linux/sockptr.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h index 3e6c8e9d67ae..ba88f4d78c1b 100644 --- a/include/linux/sockptr.h +++ b/include/linux/sockptr.h @@ -91,7 +91,7 @@ static inline int copy_struct_from_sockptr(void *dst, size_t ksize, size_t rest = max(ksize, usize) - size; if (!sockptr_is_kernel(src)) - return copy_struct_from_user(dst, ksize, src.user, size); + return copy_struct_from_user(dst, ksize, src.user, usize); if (usize < ksize) { memset(dst + size, 0, rest); From 2eef8b32e4c84caa927495f1d9bc9529d2bc5ac6 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Tue, 7 Apr 2026 18:03:15 +0200 Subject: [PATCH 3/5] uaccess: add copy_struct_{from,to}_bounce_buffer() helpers These are similar to copy_struct_{from,to}_user() but operate on kernel buffers instead of user buffers. They can be used when there is a temporary bounce buffer used, e.g. in msg_control or similar places. It allows us to have the same logic to handle old vs. current and current vs. new structures in the same compatible way. copy_struct_from_sockptr() will also be able to use copy_struct_from_bounce_buffer() for the kernel case as follow us patch. I'll use this in my IPPROTO_SMBDIRECT work, but maybe it will also be useful for others... IPPROTO_QUIC will likely also use it. Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Dmitry Safonov Cc: Francesco Ruggeri Cc: Salam Noureddine Cc: David Ahern Cc: David S. Miller Cc: Michal Luczaj Cc: David Wei Cc: Luiz Augusto von Dentz Cc: Luiz Augusto von Dentz Cc: Marcel Holtmann Cc: Xin Long Cc: Eric Dumazet Cc: Kuniyuki Iwashima Cc: Paolo Abeni Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Jakub Kicinski Cc: Simon Horman Cc: Aleksa Sarai Cc: Christian Brauner CC: Kees Cook Cc: netdev@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Stefan Metzmacher Link: https://patch.msgid.link/f29570914590c50b9b6f451eb3a38d0fe1d954df.1775576651.git.metze@samba.org Signed-off-by: Christian Brauner --- include/linux/uaccess.h | 63 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 63 insertions(+) diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 09a09cc4aac2..e4a64976f1c5 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -518,6 +518,69 @@ copy_struct_to_user(void __user *dst, size_t usize, const void *src, return 0; } +static __always_inline void +__copy_struct_generic_bounce_buffer(void *dst, size_t dstsize, + const void *src, size_t srcsize, + bool *ignored_trailing) +{ + size_t size = min(dstsize, srcsize); + size_t rest = max(dstsize, srcsize) - size; + + /* Deal with trailing bytes. */ + if (dstsize > srcsize) + memset(dst + size, 0, rest); + if (ignored_trailing) + *ignored_trailing = dstsize < srcsize && + memchr_inv(src + size, 0, rest) != NULL; + /* Copy the interoperable parts of the struct. */ + memcpy(dst, src, size); +} + +/** + * This is like copy_struct_from_user(), but the + * src buffer was already copied into a kernel + * bounce buffer, so it will never return -EFAULT. + */ +static __always_inline __must_check int +copy_struct_from_bounce_buffer(void *dst, size_t dstsize, + const void *src, size_t srcsize) +{ + bool ignored_trailing; + + /* Double check if ksize is larger than a known object size. */ + if (WARN_ON_ONCE(dstsize > __builtin_object_size(dst, 1))) + return -E2BIG; + + __copy_struct_generic_bounce_buffer(dst, dstsize, + src, srcsize, + &ignored_trailing); + if (unlikely(ignored_trailing)) + return -E2BIG; + + return 0; +} + +/** + * This is like copy_struct_to_user(), but the + * dst buffer is a kernel bounce buffer instead + * of a direct userspace buffer, so it will never return -EFAULT. + */ +static __always_inline __must_check int +copy_struct_to_bounce_buffer(void *dst, size_t dstsize, + const void *src, + size_t srcsize, + bool *ignored_trailing) +{ + /* Double check if srcsize is larger than a known object size. */ + if (WARN_ON_ONCE(srcsize > __builtin_object_size(src, 1))) + return -E2BIG; + + __copy_struct_generic_bounce_buffer(dst, dstsize, + src, srcsize, + ignored_trailing); + return 0; +} + bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size); long copy_from_kernel_nofault(void *dst, const void *src, size_t size); From d2c344740bf9e54c91d8d4a99bfe5fc1709a3ecc Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Tue, 7 Apr 2026 18:03:16 +0200 Subject: [PATCH 4/5] sockptr: let copy_struct_from_sockptr() use copy_struct_from_bounce_buffer() The world would be better without sockptr_t, but this at least simplifies copy_struct_from_sockptr() to be just a dispatcher for copy_struct_from_user() or copy_struct_from_bounce_buffer() without any special logic on its own. Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Dmitry Safonov Cc: Francesco Ruggeri Cc: Salam Noureddine Cc: David Ahern Cc: David S. Miller Cc: Michal Luczaj Cc: David Wei Cc: Luiz Augusto von Dentz Cc: Luiz Augusto von Dentz Cc: Marcel Holtmann Cc: Xin Long Cc: Eric Dumazet Cc: Kuniyuki Iwashima Cc: Paolo Abeni Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Jakub Kicinski Cc: Simon Horman Cc: Aleksa Sarai Cc: Christian Brauner CC: Kees Cook Cc: netdev@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Stefan Metzmacher Link: https://patch.msgid.link/b9b7e22664a53251d7ad099b12aead8b599c1257.1775576651.git.metze@samba.org Signed-off-by: Christian Brauner --- include/linux/sockptr.h | 16 +--------------- 1 file changed, 1 insertion(+), 15 deletions(-) diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h index ba88f4d78c1b..706a8526cf3c 100644 --- a/include/linux/sockptr.h +++ b/include/linux/sockptr.h @@ -87,24 +87,10 @@ static inline int copy_safe_from_sockptr(void *dst, size_t ksize, static inline int copy_struct_from_sockptr(void *dst, size_t ksize, sockptr_t src, size_t usize) { - size_t size = min(ksize, usize); - size_t rest = max(ksize, usize) - size; - if (!sockptr_is_kernel(src)) return copy_struct_from_user(dst, ksize, src.user, usize); - if (usize < ksize) { - memset(dst + size, 0, rest); - } else if (usize > ksize) { - char *p = src.kernel; - - while (rest--) { - if (*p++) - return -E2BIG; - } - } - memcpy(dst, src.kernel, size); - return 0; + return copy_struct_from_bounce_buffer(dst, ksize, src.kernel, usize); } static inline int copy_to_sockptr_offset(sockptr_t dst, size_t offset, From c5ca9f85d7fe27a8c9c88195bb819e8b569fa930 Mon Sep 17 00:00:00 2001 From: Stefan Metzmacher Date: Tue, 7 Apr 2026 18:03:17 +0200 Subject: [PATCH 5/5] sockptr: introduce copy_struct_to_sockptr() We already have copy_struct_from_sockptr() as wrapper to copy_struct_from_user() or copy_struct_from_bounce_buffer(), so it's good to have copy_struct_to_sockptr() as well matching the behavior of copy_struct_to_user() or copy_struct_to_bounce_buffer(). The world would be better without sockptr_t, but having copy_struct_to_sockptr() is better than open code it in various places. I'll use this in my IPPROTO_SMBDIRECT work, but maybe it will also be useful for others... IPPROTO_QUIC will likely also use it. Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: Dmitry Safonov Cc: Francesco Ruggeri Cc: Salam Noureddine Cc: David Ahern Cc: David S. Miller Cc: Michal Luczaj Cc: David Wei Cc: Luiz Augusto von Dentz Cc: Luiz Augusto von Dentz Cc: Marcel Holtmann Cc: Xin Long Cc: Eric Dumazet Cc: Kuniyuki Iwashima Cc: Paolo Abeni Cc: Willem de Bruijn Cc: Neal Cardwell Cc: Jakub Kicinski Cc: Simon Horman Cc: Aleksa Sarai Cc: Christian Brauner CC: Kees Cook Cc: netdev@vger.kernel.org Cc: linux-bluetooth@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Stefan Metzmacher Link: https://patch.msgid.link/c950ee1578cb93b4411c3731010def9c1cd82f0d.1775576651.git.metze@samba.org Signed-off-by: Christian Brauner --- include/linux/sockptr.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/sockptr.h b/include/linux/sockptr.h index 706a8526cf3c..9c2429c1a570 100644 --- a/include/linux/sockptr.h +++ b/include/linux/sockptr.h @@ -107,6 +107,16 @@ static inline int copy_to_sockptr(sockptr_t dst, const void *src, size_t size) return copy_to_sockptr_offset(dst, 0, src, size); } +static inline int +copy_struct_to_sockptr(sockptr_t dst, size_t usize, const void *src, + size_t ksize, bool *ignored_trailing) +{ + if (!sockptr_is_kernel(dst)) + return copy_struct_to_user(dst.user, usize, src, ksize, ignored_trailing); + + return copy_struct_to_bounce_buffer(dst.kernel, usize, src, ksize, ignored_trailing); +} + static inline void *memdup_sockptr_noprof(sockptr_t src, size_t len) { void *p = kmalloc_track_caller_noprof(len, GFP_USER | __GFP_NOWARN);