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authorJason A. Donenfeld <Jason@zx2c4.com>2017-06-04 04:16:22 +0200
committerDavid S. Miller <davem@davemloft.net>2017-06-04 23:01:47 -0400
commit48a1df65334b74bd7531f932cca5928932abf769 (patch)
treeda1baab25c096414f2af17e97dbec7172426f53d /net/ipv4/ah4.c
parentMerge branch 'bpf-Add-BPF-support-to-all-perf_event' (diff)
downloadlinux-dev-48a1df65334b74bd7531f932cca5928932abf769.tar.xz
linux-dev-48a1df65334b74bd7531f932cca5928932abf769.zip
skbuff: return -EMSGSIZE in skb_to_sgvec to prevent overflow
This is a defense-in-depth measure in response to bugs like 4d6fa57b4dab ("macsec: avoid heap overflow in skb_to_sgvec"). There's not only a potential overflow of sglist items, but also a stack overflow potential, so we fix this by limiting the amount of recursion this function is allowed to do. Not actually providing a bounded base case is a future disaster that we can easily avoid here. As a small matter of house keeping, we take this opportunity to move the documentation comment over the actual function the documentation is for. While this could be implemented by using an explicit stack of skbuffs, when implementing this, the function complexity increased considerably, and I don't think such complexity and bloat is actually worth it. So, instead I built this and tested it on x86, x86_64, ARM, ARM64, and MIPS, and measured the stack usage there. I also reverted the recent MIPS changes that give it a separate IRQ stack, so that I could experience some worst-case situations. I found that limiting it to 24 layers deep yielded a good stack usage with room for safety, as well as being much deeper than any driver actually ever creates. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: "David S. Miller" <davem@davemloft.net> Cc: David Howells <dhowells@redhat.com> Cc: Sabrina Dubroca <sd@queasysnail.net> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ah4.c')
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