NACK: [PATCH 0/3][B/G/oem-5.6] CVE-2021-29650: xtables membarrier DoS

[Tim Gardner]

I'll resubmit a v2 of this series with the Groovy (Revert "netfilter: 
x_tables: Switch synchronization to RCU") applied per Kamal's suggestion.

rtg

On 4/6/21 8:45 AM, Tim Gardner wrote:
> [SRU Justification]
> 
> An issue was discovered in the Linux kernel before 5.11.11. The netfilter
> subsystem allows attackers to cause a denial of service (panic) because
> net/netfilter/x_tables.c and include/linux/netfilter/x_tables.h lack a
> full memory barrier upon the assignment of a new table value, aka CID-175e476b8cdf.
> 
> This DOS has existed since v3.0. It was partially mitigated by
> cc00bcaa589914096edef7fb87ca5cee4a166b5c ("netfilter: x_tables: Switch
> synchronization to RCU") in v5.10, but was then reverted in v5.12 which restored the
> full DOS vulnerability. Hence the fix commit 175e476b8cdf2a4de7432583b49c871345e4f8a1
> in v5.12.
> 
> Focal, Hirsute, and oem-5.10 will get this patch via stable updates.
> 
> [Test Plan]
> 
> None
> 
> [Where problems could occur]
> Released in stable updates:
> linux-4.19.y
> linux-5.10.y
> linux-5.11.y
> linux-5.4.y
> 
> At most this patch might introduce a performance reduction, though
> upstream testing has not been able to detect any.
> 
> [Other Info]
> None
> 

-- 
-----------
Tim Gardner
Canonical, Inc