In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue<\/p>\n
gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a packet when the
\ncurrent backlog plus the packet length fits within the queue limit:<\/p>\n
sch->qstats.backlog + qdisc_pkt_len(skb) limit (gred default VQ)
\n gred_backlog+qdisc_pkt_len(skb) limit (gred configured VQ)
\n sch->qstats.backlog + qdisc_pkt_len(skb) limit (bfifo)
\n sch->qstats.backlog + skb->len limit (plug)<\/p>\n
sch->qstats.backlog and q->backlog are u32, and qdisc_pkt_len()\/skb->len
\nare unsigned int, so all sums are computed in 32 bits and wrap at 2^32.
\nOnce the true backlog exceeds 4 GiB the wrapped sum becomes small and
\nadmission keeps succeeding, so the queue grows without bound and the kernel
\ncan be driven to OOM.<\/p>\n
Promote the sums to u64 so admission stops once the true backlog exceeds
\nthe limit. The limit is u32, so the bounded queue stays below 2^32 and
\nthe stored u32 backlog never wraps.<\/p>\n
The bug can only be reproduced as root (albeit with ridiculous setup):
\n attach a gred (or bfifo\/plug) qdisc with a limit near 4 GiB,
\n leaving the default VQ unconfigured (for gred), and drive >4 GiB of
\n queued traffic (e.g. via a size table \/ stab to inflate qdisc_pkt_len,
\n or sustained high-rate traffic). The u32 backlog+len sum wraps at 2^32,
\n admission keeps succeeding, and the queue grows unboundedly to OOM.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
net: sched: fix 32-bit backlog wrap in gred, bfifo and plug enqueue<\/p>\n
gred_enqueue(), bfifo_enqueue() and plug_enqueue() admit a pac<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-25518","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/25518","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=25518"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=25518"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=25518"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}