bpf, x32: Fix regression caused by commit 24dea04767e6

Commit 24dea04767e6 ("bpf, x32: remove ld_abs/ld_ind")
removed the 4 /* Extra space for skb_copy_bits buffer */
from _STACK_SIZE, but it didn't fix the concerned code
in emit_prologue and emit_epilogue, and this error will
bring very strange kernel runtime errors. This patch
fixes it.

Fixes: 24dea04767e6 ("bpf, x32: remove ld_abs/ld_ind")
Reported-by: Meelis Roos <mroos@linux.ee>
Bisected-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Wang YanQing <udknight@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c
index 55799873ebe5..8f6cc71e0848 100644
--- a/arch/x86/net/bpf_jit_comp32.c
+++ b/arch/x86/net/bpf_jit_comp32.c
@@ -1441,8 +1441,8 @@ static void emit_prologue(u8 **pprog, u32 stack_depth)
 
         /* sub esp,STACK_SIZE */
         EMIT2_off32(0x81, 0xEC, STACK_SIZE);
-        /* sub ebp,SCRATCH_SIZE+4+12*/
-        EMIT3(0x83, add_1reg(0xE8, IA32_EBP), SCRATCH_SIZE + 16);
+        /* sub ebp,SCRATCH_SIZE+12*/
+        EMIT3(0x83, add_1reg(0xE8, IA32_EBP), SCRATCH_SIZE + 12);
         /* xor ebx,ebx */
         EMIT2(0x31, add_2reg(0xC0, IA32_EBX, IA32_EBX));
 
@@ -1475,8 +1475,8 @@ static void emit_epilogue(u8 **pprog, u32 stack_depth)
         /* mov edx,dword ptr [ebp+off]*/
         EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EDX), STACK_VAR(r0[1]));
 
-        /* add ebp,SCRATCH_SIZE+4+12*/
-        EMIT3(0x83, add_1reg(0xC0, IA32_EBP), SCRATCH_SIZE + 16);
+        /* add ebp,SCRATCH_SIZE+12*/
+        EMIT3(0x83, add_1reg(0xC0, IA32_EBP), SCRATCH_SIZE + 12);
 
         /* mov ebx,dword ptr [ebp-12]*/
         EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_EBX), -12);