| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.18 022/123] bpf, arm32: fix stack var offset in jit | Date | Mon, 3 Sep 2018 18:56:06 +0200 |
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4.18-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Borkmann <daniel@iogearbox.net>
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> --- arch/arm/net/bpf_jit_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -238,7 +238,7 @@ static void jit_fill_hole(void *area, un #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
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