In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ipv6: account for fraggap on the paged allocation path<\/p>\n
In __ip6_append_data(), when the paged-allocation branch is taken
\n(MSG_MORE \/ NETIF_F_SG \/ large fraglen), alloclen and pagedlen are
\ncomputed as<\/p>\n
\talloclen = fragheaderlen + transhdrlen;
\n\tpagedlen = datalen – transhdrlen;<\/p>\n
datalen already includes fraggap (datalen = length + fraggap). When
\nfraggap is non-zero, this is not the first skb and transhdrlen is zero.
\nThe fraggap bytes carried over from the previous skb are copied just past
\nthe fragment headers in the new skb’s linear area. The linear area is
\ntherefore undersized by fraggap bytes while pagedlen is overstated by the
\nsame amount, and the copy writes past skb->end into the trailing
\nskb_shared_info.<\/p>\n
An unprivileged user can trigger this via a UDPv6 socket using
\nMSG_MORE together with MSG_SPLICE_PAGES.<\/p>\n
The bad accounting was introduced by commit 773ba4fe9104 (“ipv6:
\navoid partial copy for zc”). Before commit ce650a166335 (“udp6: Fix
\n__ip6_append_data()’s handling of MSG_SPLICE_PAGES”), the negative
\ncopy value caused -EINVAL to be returned. That later commit allowed
\nMSG_SPLICE_PAGES to proceed in this case, making the corruption
\ntriggerable.<\/p>\n
The non-paged branch sets alloclen to fraglen, which already accounts
\nfor fraggap because datalen does. Bring the paged branch in line by
\nadding fraggap to alloclen and subtracting it from pagedlen.<\/p>\n
After this adjustment, copy no longer collapses to -fraggap on the
\npaged path, so remove the stale comment describing that old arithmetic.
\nSince a negative copy is no longer expected for a valid MSG_SPLICE_PAGES
\ncase, remove the MSG_SPLICE_PAGES exception from the negative copy check.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
ipv6: account for fraggap on the paged allocation path<\/p>\n
In __ip6_append_data(), when the paged-allocation branch is taken
\n(MSG_MORE<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-12898","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/12898","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=12898"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=12898"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=12898"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}