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Subject[ 097/108] net: bpf_jit: fix BPF_S_LDX_B_MSH compilation
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <eric.dumazet@gmail.com>

[ Upstream commit dc72d99dabb870ca5bd6d9fff674be853bb4a88d ]

Matt Evans spotted that x86 bpf_jit was incorrectly handling negative
constant offsets in BPF_S_LDX_B_MSH instruction.

We need to abort JIT compilation like we do in common_load so that
filter uses the interpreter code and can call __load_pointer()

Reference: http://lists.openwall.net/netdev/2011/07/19/11

Thanks to Indan Zupancic to bring back this issue.

Reported-by: Matt Evans <matt@ozlabs.org>
Reported-by: Indan Zupancic <indan@nul.nu>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/net/bpf_jit_comp.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -475,8 +475,10 @@ void bpf_jit_compile(struct sk_filter *f
case BPF_S_LD_W_ABS:
func = sk_load_word;
common_load: seen |= SEEN_DATAREF;
- if ((int)K < 0)
+ if ((int)K < 0) {
+ /* Abort the JIT because __load_pointer() is needed. */
goto out;
+ }
t_offset = func - (image + addrs[i]);
EMIT1_off32(0xbe, K); /* mov imm32,%esi */
EMIT1_off32(0xe8, t_offset); /* call */
@@ -489,14 +491,8 @@ common_load: seen |= SEEN_DATAREF;
goto common_load;
case BPF_S_LDX_B_MSH:
if ((int)K < 0) {
- if (pc_ret0 > 0) {
- /* addrs[pc_ret0 - 1] is the start address */
- EMIT_JMP(addrs[pc_ret0 - 1] - addrs[i]);
- break;
- }
- CLEAR_A();
- EMIT_JMP(cleanup_addr - addrs[i]);
- break;
+ /* Abort the JIT because __load_pointer() is needed. */
+ goto out;
}
seen |= SEEN_DATAREF | SEEN_XREG;
t_offset = sk_load_byte_msh - (image + addrs[i]);



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