[PATCH 3.19.y-ckt 043/146] arm64: bpf: fix signedness bug in loading 64-bit immediate

From: Kamal Mostafa
Date: Wed Jun 17 2015 - 19:35:10 EST

3.19.8-ckt2 -stable review patch. If anyone has any objections, please let me know.


From: Xi Wang <xi.wang@xxxxxxxxx>

commit 1e4df6b7208140f3c49f316d33a409d3a161f350 upstream.

Consider "(u64)insn1.imm << 32 | imm" in the arm64 JIT. Since imm is
signed 32-bit, it is sign-extended to 64-bit, losing the high 32 bits.
The fix is to convert imm to u32 first, which will be zero-extended to
u64 implicitly.

Cc: Zi Shen Lim <zlim.lnx@xxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Fixes: 30d3d94cc3d5 ("arm64: bpf: add 'load 64-bit immediate' instruction")
Signed-off-by: Xi Wang <xi.wang@xxxxxxxxx>
[will: removed non-arm64 bits and redundant casting]
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
arch/arm64/net/bpf_jit_comp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index edba042..dc6a484 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -487,7 +487,7 @@ emit_cond_jmp:
return -EINVAL;

- imm64 = (u64)insn1.imm << 32 | imm;
+ imm64 = (u64)insn1.imm << 32 | (u32)imm;
emit_a64_mov_i64(dst, imm64, ctx);

return 1;

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