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bpf, arm32: fix stack var offset in jit

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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>
This commit is contained in:
Daniel Borkmann 2018-08-18 00:21:34 +02:00 committed by Greg Kroah-Hartman
parent 6289b80699
commit 29ac604e62
1 changed files with 1 additions and 1 deletions
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arch/arm/net/bpf_jit_32.c
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@ -238,7 +238,7 @@ static void jit_fill_hole(void *area, unsigned int size)
#define STACK_SIZE ALIGN(_STACK_SIZE, STACK_ALIGNMENT)
/* Get the offset of eBPF REGISTERs stored on scratch space. */
#define STACK_VAR(off) (STACK_SIZE - off)
#define STACK_VAR(off) (STACK_SIZE - off - 4)
#if __LINUX_ARM_ARCH__ < 7