6.12-stable review patch. If anyone has any objections, please let me know.
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From: Pedro Falcato pfalcato@suse.de
commit c18646248fed07683d4cee8a8af933fc4fe83c0d upstream.
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.
Link: https://patch.msgid.link/r/20250729120348.495568-1-pfalcato@suse.de Cc: stable@vger.kernel.org Fixes: c2ff29e99a76 ("siw: Inline do_tcp_sendpages()") Reported-by: kernel test robot oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202507220801.50a7210-lkp@intel.com Reviewed-by: David Howells dhowells@redhat.com Signed-off-by: Pedro Falcato pfalcato@suse.de Acked-by: Bernard Metzler bernard.metzler@linux.dev Signed-off-by: Jason Gunthorpe jgg@nvidia.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/infiniband/sw/siw/siw_qp_tx.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
--- a/drivers/infiniband/sw/siw/siw_qp_tx.c +++ b/drivers/infiniband/sw/siw/siw_qp_tx.c @@ -334,18 +334,17 @@ static int siw_tcp_sendpages(struct sock if (!sendpage_ok(page[i])) msg.msg_flags &= ~MSG_SPLICE_PAGES; bvec_set_page(&bvec, page[i], bytes, offset); - iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, size); + iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, &bvec, 1, bytes);
try_page_again: lock_sock(sk); - rv = tcp_sendmsg_locked(sk, &msg, size); + rv = tcp_sendmsg_locked(sk, &msg, bytes); release_sock(sk);
if (rv > 0) { size -= rv; sent += rv; if (rv != bytes) { - offset += rv; bytes -= rv; goto try_page_again; }