In the Linux kernel, the following vulnerability has been resolved:
RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"),
we have been doing this:
static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,
size_t size)
[...]
/* Calculate the number of bytes we need to push, for this page
* specifically */
size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);
/* If we can't splice it, then copy it in, as normal */
if (!sendpage_ok(page[i]))
msg.msg_flags &= ~MSG_SPLICE_PAGES;
/* Set the bvec pointing to the page, with len $bytes */
bvec_set_page(&bvec, page[i], bytes, offset);
/* Set the iter to $size, aka the size of the whole sendpages (!!!) */
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
try_page_again:
lock_sock(sk);
/* Sendmsg with $size size (!!!) */
rv = tcp_sendmsg_locked(sk, &msg, size);
This means we've been sending oversized iov_iters and tcp_sendmsg calls
for a while. This has a been a benign bug because sendpage_ok() always
returned true. With the recent slab allocator changes being slowly
introduced into next (that disallow sendpage on large kmalloc
allocations), we have recently hit out-of-bounds crashes, due to slight
differences in iov_iter behavior between the MSG_SPLICE_PAGES and
"regular" copy paths:
(MSG_SPLICE_PAGES)
skb_splice_from_iter
iov_iter_extract_pages
iov_iter_extract_bvec_pages
uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere
skb_splice_from_iter gets a "short" read
(!MSG_SPLICE_PAGES)
skb_copy_to_page_nocache copy=iov_iter_count
[...]
copy_from_iter
/* this doesn't help */
if (unlikely(iter->count < len))
len = iter->count;
iterate_bvec
... and we run off the bvecs
Fix this by properly setting the iov_iter's byte count, plus sending the
correct byte count to tcp_sendmsg_locked.
RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages
Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"),
we have been doing this:
static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset,
size_t size)
[...]
/* Calculate the number of bytes we need to push, for this page
* specifically */
size_t bytes = min_t(size_t, PAGE_SIZE - offset, size);
/* If we can't splice it, then copy it in, as normal */
if (!sendpage_ok(page[i]))
msg.msg_flags &= ~MSG_SPLICE_PAGES;
/* Set the bvec pointing to the page, with len $bytes */
bvec_set_page(&bvec, page[i], bytes, offset);
/* Set the iter to $size, aka the size of the whole sendpages (!!!) */
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size);
try_page_again:
lock_sock(sk);
/* Sendmsg with $size size (!!!) */
rv = tcp_sendmsg_locked(sk, &msg, size);
This means we've been sending oversized iov_iters and tcp_sendmsg calls
for a while. This has a been a benign bug because sendpage_ok() always
returned true. With the recent slab allocator changes being slowly
introduced into next (that disallow sendpage on large kmalloc
allocations), we have recently hit out-of-bounds crashes, due to slight
differences in iov_iter behavior between the MSG_SPLICE_PAGES and
"regular" copy paths:
(MSG_SPLICE_PAGES)
skb_splice_from_iter
iov_iter_extract_pages
iov_iter_extract_bvec_pages
uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere
skb_splice_from_iter gets a "short" read
(!MSG_SPLICE_PAGES)
skb_copy_to_page_nocache copy=iov_iter_count
[...]
copy_from_iter
/* this doesn't help */
if (unlikely(iter->count < len))
len = iter->count;
iterate_bvec
... and we run off the bvecs
Fix this by properly setting the iov_iter's byte count, plus sending the
correct byte count to tcp_sendmsg_locked.
Metrics
Affected Vendors & Products
No data.
No data.
No data.
No data.
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 11 Sep 2025 17:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages Ever since commit c2ff29e99a76 ("siw: Inline do_tcp_sendpages()"), we have been doing this: static int siw_tcp_sendpages(struct socket *s, struct page **page, int offset, size_t size) [...] /* Calculate the number of bytes we need to push, for this page * specifically */ size_t bytes = min_t(size_t, PAGE_SIZE - offset, size); /* If we can't splice it, then copy it in, as normal */ if (!sendpage_ok(page[i])) msg.msg_flags &= ~MSG_SPLICE_PAGES; /* Set the bvec pointing to the page, with len $bytes */ bvec_set_page(&bvec, page[i], bytes, offset); /* Set the iter to $size, aka the size of the whole sendpages (!!!) */ iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size); try_page_again: lock_sock(sk); /* Sendmsg with $size size (!!!) */ rv = tcp_sendmsg_locked(sk, &msg, size); This means we've been sending oversized iov_iters and tcp_sendmsg calls for a while. This has a been a benign bug because sendpage_ok() always returned true. With the recent slab allocator changes being slowly introduced into next (that disallow sendpage on large kmalloc allocations), we have recently hit out-of-bounds crashes, due to slight differences in iov_iter behavior between the MSG_SPLICE_PAGES and "regular" copy paths: (MSG_SPLICE_PAGES) skb_splice_from_iter iov_iter_extract_pages iov_iter_extract_bvec_pages uses i->nr_segs to correctly stop in its tracks before OoB'ing everywhere skb_splice_from_iter gets a "short" read (!MSG_SPLICE_PAGES) skb_copy_to_page_nocache copy=iov_iter_count [...] copy_from_iter /* this doesn't help */ if (unlikely(iter->count < len)) len = iter->count; iterate_bvec ... and we run off the bvecs Fix this by properly setting the iov_iter's byte count, plus sending the correct byte count to tcp_sendmsg_locked. | |
| Title | RDMA/siw: Fix the sendmsg byte count in siw_tcp_sendpages | |
| References |
|
|
MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2025-09-11T16:52:27.598Z
Reserved: 2025-04-16T07:20:57.125Z
Link: CVE-2025-39758
Vulnrichment
No data.
NVD
Status : Received
Published: 2025-09-11T17:15:39.663
Modified: 2025-09-11T17:15:39.663
Link: CVE-2025-39758
Redhat
No data.
OpenCVE Enrichment
No data.