From a31196b07f8034eba6a3487a1ad1bb5ec5cd58a5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sat, 25 Apr 2015 09:35:24 -0700 Subject: net: rfs: fix crash in get_rps_cpus() Commit 567e4b79731c ("net: rfs: add hash collision detection") had one mistake : RPS_NO_CPU is no longer the marker for invalid cpu in set_rps_cpu() and get_rps_cpu(), as @next_cpu was the result of an AND with rps_cpu_mask This bug showed up on a host with 72 cpus : next_cpu was 0x7f, and the code was trying to access percpu data of an non existent cpu. In a follow up patch, we might get rid of compares against nr_cpu_ids, if we init the tables with 0. This is silly to test for a very unlikely condition that exists only shortly after table initialization, as we got rid of rps_reset_sock_flow() and similar functions that were writing this RPS_NO_CPU magic value at flow dismantle : When table is old enough, it never contains this value anymore. Fixes: 567e4b79731c ("net: rfs: add hash collision detection") Signed-off-by: Eric Dumazet Cc: Tom Herbert Cc: Ben Hutchings Signed-off-by: David S. Miller --- Documentation/networking/scaling.txt | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation/networking') diff --git a/Documentation/networking/scaling.txt b/Documentation/networking/scaling.txt index cbfac0949635..59f4db2a0c85 100644 --- a/Documentation/networking/scaling.txt +++ b/Documentation/networking/scaling.txt @@ -282,7 +282,7 @@ following is true: - The current CPU's queue head counter >= the recorded tail counter value in rps_dev_flow[i] -- The current CPU is unset (equal to RPS_NO_CPU) +- The current CPU is unset (>= nr_cpu_ids) - The current CPU is offline After this check, the packet is sent to the (possibly updated) current -- cgit v1.2.3