Merge tag 'for-f2fs-4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk...

[karo-tx-linux.git] / arch / mips / net / bpf_jit.c

diff --git a/arch/mips/net/bpf_jit.c b/arch/mips/net/bpf_jit.c
index a68cd36a892f2a7bcc08968eaced775aae60a228..44b925005dd37c78d8c85a814bef8ed69c927522 100644 (file)
--- a/arch/mips/net/bpf_jit.c
+++ b/arch/mips/net/bpf_jit.c
@@ -532,7 +532,8 @@ static void save_bpf_jit_regs(struct jit_ctx *ctx, unsigned offset)
        u32 sflags, tmp_flags;
 
        /* Adjust the stack pointer */
-       emit_stack_offset(-align_sp(offset), ctx);
+       if (offset)
+               emit_stack_offset(-align_sp(offset), ctx);
 
        tmp_flags = sflags = ctx->flags >> SEEN_SREG_SFT;
        /* sflags is essentially a bitmap */
@@ -584,7 +585,8 @@ static void restore_bpf_jit_regs(struct jit_ctx *ctx,
                emit_load_stack_reg(r_ra, r_sp, real_off, ctx);
 
        /* Restore the sp and discard the scrach memory */
-       emit_stack_offset(align_sp(offset), ctx);
+       if (offset)
+               emit_stack_offset(align_sp(offset), ctx);
 }
 
 static unsigned int get_stack_depth(struct jit_ctx *ctx)
@@ -631,8 +633,14 @@ static void build_prologue(struct jit_ctx *ctx)
        if (ctx->flags & SEEN_X)
                emit_jit_reg_move(r_X, r_zero, ctx);
 
-       /* Do not leak kernel data to userspace */
-       if (bpf_needs_clear_a(&ctx->skf->insns[0]))
+       /*
+        * Do not leak kernel data to userspace, we only need to clear
+        * r_A if it is ever used.  In fact if it is never used, we
+        * will not save/restore it, so clearing it in this case would
+        * corrupt the state of the caller.
+        */
+       if (bpf_needs_clear_a(&ctx->skf->insns[0]) &&
+           (ctx->flags & SEEN_A))
                emit_jit_reg_move(r_A, r_zero, ctx);
 }