On Sat, Aug 18, 2018 at 12:21:34AM +0200, Daniel Borkmann wrote:
Commit 38ca93060163 ("bpf, arm32: save 4 bytes of unneeded stack space") messed up STACK_VAR() by 4 bytes presuming it was related to skb scratch buffer space, but it clearly isn't as this refers to the top word in stack, therefore restore it. This fixes a NULL pointer dereference seen during bootup when JIT is enabled and BPF program run in sk_filter_trim_cap() triggered by systemd-udevd.
JIT rework in 1c35ba122d4a ("ARM: net: bpf: use negative numbers for stacked registers") and 96cced4e774a ("ARM: net: bpf: access eBPF scratch space using ARM FP register") removed the affected parts, so only needed in 4.18 stable.
Fixes: 38ca93060163 ("bpf, arm32: save 4 bytes of unneeded stack space") Reported-by: Peter Robinson pbrobinson@gmail.com Reported-by: Marc Haber mh+netdev@zugschlus.de Tested-by: Stefan Wahren stefan.wahren@i2se.com Tested-by: Peter Robinson pbrobinson@gmail.com Cc: Russell King rmk+kernel@armlinux.org.uk Cc: Alexei Starovoitov ast@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net
Acked-by: Alexei Starovoitov ast@kernel.org