[PATCH v2 14/17] MIPS: bpf: Prevent kernel fall over for >=32bit shifts
From: Markos Chandras <hidden>
Date: 2014-06-25 08:37:34
Also in:
linux-mips
Subsystem:
bpf jit for mips (32-bit and 64-bit), bpf [general] (safe dynamic programs and tools), mips, the rest · Maintainers:
Johan Almbladh, Paul Burton, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Thomas Bogendoerfer, Linus Torvalds
Remove BUG_ON() if the shift immediate is >=32 to avoid kernel crashes due to malicious user input. If the shift immediate is >= 32, we simply load the destination register with 0 since only 32-bit instructions are used by JIT so this will do the correct thing even on MIPS64. Cc: "David S. Miller" <davem@davemloft.net> Cc: Daniel Borkmann <redacted> Cc: Alexei Starovoitov <redacted> Cc: netdev@vger.kernel.org Signed-off-by: Markos Chandras <redacted> --- Changes since v1: - For sa >=32, load destination register with zero instead of treating the immediate as 31 --- arch/mips/net/bpf_jit.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index 1bcd599d9971..9476e7f061a1 100644
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c@@ -151,6 +151,8 @@ static inline int optimize_div(u32 *k) return 0; } +static inline void emit_jit_reg_move(ptr dst, ptr src, struct jit_ctx *ctx); + /* Simply emit the instruction if the JIT memory space has been allocated */ #define emit_instr(ctx, func, ...) \ do { \
@@ -309,8 +311,11 @@ static inline void emit_sll(unsigned int dst, unsigned int src, unsigned int sa, struct jit_ctx *ctx) { /* sa is 5-bits long */ - BUG_ON(sa >= BIT(5)); - emit_instr(ctx, sll, dst, src, sa); + if (sa >= BIT(5)) + /* Shifting >= 32 results in zero */ + emit_jit_reg_move(dst, r_zero, ctx); + else + emit_instr(ctx, sll, dst, src, sa); } static inline void emit_srlv(unsigned int dst, unsigned int src,
@@ -323,8 +328,11 @@ static inline void emit_srl(unsigned int dst, unsigned int src, unsigned int sa, struct jit_ctx *ctx) { /* sa is 5-bits long */ - BUG_ON(sa >= BIT(5)); - emit_instr(ctx, srl, dst, src, sa); + if (sa >= BIT(5)) + /* Shifting >= 32 results in zero */ + emit_jit_reg_move(dst, r_zero, ctx); + else + emit_instr(ctx, srl, dst, src, sa); } static inline void emit_slt(unsigned int dst, unsigned int src1,
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2.0.0