4.0-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nicolas Schichan <nschic...@freebox.fr>
commit 19fc99d0c6ba7d9b65456496b5bb2169d5f74cd0 upstream.
In that case, emit_udiv() will be called with rn == ARM_R0 (r_scratch)
and loading rm first into ARM_R0 will result in jit_udiv() function
being called the same dividend and divisor. Fix that by loading rn
first into ARM_R1 and then rm into ARM_R0.
Signed-off-by: Nicolas Schichan <nschic...@freebox.fr>
Fixes: aee636c4809f (bpf: do not use reciprocal divide)
Acked-by: Mircea Gherzan <mgher...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
arch/arm/net/bpf_jit_32.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -449,10 +449,21 @@ static inline void emit_udiv(u8 rd, u8 r
return;
}
#endif
- if (rm != ARM_R0)
- emit(ARM_MOV_R(ARM_R0, rm), ctx);
+
+ /*
+ * For BPF_ALU | BPF_DIV | BPF_K instructions, rm is ARM_R4
+ * (r_A) and rn is ARM_R0 (r_scratch) so load rn first into
+ * ARM_R1 to avoid accidentally overwriting ARM_R0 with rm
+ * before using it as a source for ARM_R1.
+ *
+ * For BPF_ALU | BPF_DIV | BPF_X rm is ARM_R4 (r_A) and rn is
+ * ARM_R5 (r_X) so there is no particular register overlap
+ * issues.
+ */
if (rn != ARM_R1)
emit(ARM_MOV_R(ARM_R1, rn), ctx);
+ if (rm != ARM_R0)
+ emit(ARM_MOV_R(ARM_R0, rm), ctx);
ctx->seen |= SEEN_CALL;
emit_mov_i(ARM_R3, (u32)jit_udiv, ctx);
--
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