This is a note to let you know that I've just added the patch titled
[PATCH stable/4.14 03/14] bpf, s390x: do not reload skb pointers in non-skb context
to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: bpf-s390x-do-not-reload-skb-pointers-in-non-skb-context.patch and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From foo@baz Fri Dec 22 16:47:02 CET 2017
From: Daniel Borkmann daniel@iogearbox.net Date: Fri, 22 Dec 2017 16:23:01 +0100 Subject: [PATCH stable/4.14 03/14] bpf, s390x: do not reload skb pointers in non-skb context To: gregkh@linuxfoundation.org Cc: ast@kernel.org, daniel@iogearbox.net, jannh@google.com, stable@vger.kernel.org, Michael Holzheu holzheu@linux.vnet.ibm.com Message-ID: 20171222152312.2945-4-daniel@iogearbox.net
From: Daniel Borkmann daniel@iogearbox.net
[ Upstream commit 6d59b7dbf72ed20d0138e2f9b75ca3d4a9d4faca ]
The assumption of unconditionally reloading skb pointers on BPF helper calls where bpf_helper_changes_pkt_data() holds true is wrong. There can be different contexts where the BPF helper would enforce a reload such as in case of XDP. Here, we do have a struct xdp_buff instead of struct sk_buff as context, thus this will access garbage.
JITs only ever need to deal with cached skb pointer reload when ld_abs/ind was seen, therefore guard the reload behind SEEN_SKB only. Tested on s390x.
Fixes: 9db7f2b81880 ("s390/bpf: recache skb->data/hlen for skb_vlan_push/pop") Signed-off-by: Daniel Borkmann daniel@iogearbox.net Acked-by: Alexei Starovoitov ast@kernel.org Cc: Michael Holzheu holzheu@linux.vnet.ibm.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/net/bpf_jit_comp.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)
--- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -55,8 +55,7 @@ struct bpf_jit { #define SEEN_LITERAL 8 /* code uses literals */ #define SEEN_FUNC 16 /* calls C functions */ #define SEEN_TAIL_CALL 32 /* code uses tail calls */ -#define SEEN_SKB_CHANGE 64 /* code changes skb data */ -#define SEEN_REG_AX 128 /* code uses constant blinding */ +#define SEEN_REG_AX 64 /* code uses constant blinding */ #define SEEN_STACK (SEEN_FUNC | SEEN_MEM | SEEN_SKB)
/* @@ -448,12 +447,12 @@ static void bpf_jit_prologue(struct bpf_ EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0, REG_15, 152); } - if (jit->seen & SEEN_SKB) + if (jit->seen & SEEN_SKB) { emit_load_skb_data_hlen(jit); - if (jit->seen & SEEN_SKB_CHANGE) /* stg %b1,ST_OFF_SKBP(%r0,%r15) */ EMIT6_DISP_LH(0xe3000000, 0x0024, BPF_REG_1, REG_0, REG_15, STK_OFF_SKBP); + } }
/* @@ -983,8 +982,8 @@ static noinline int bpf_jit_insn(struct EMIT2(0x0d00, REG_14, REG_W1); /* lgr %b0,%r2: load return value into %b0 */ EMIT4(0xb9040000, BPF_REG_0, REG_2); - if (bpf_helper_changes_pkt_data((void *)func)) { - jit->seen |= SEEN_SKB_CHANGE; + if ((jit->seen & SEEN_SKB) && + bpf_helper_changes_pkt_data((void *)func)) { /* lg %b1,ST_OFF_SKBP(%r15) */ EMIT6_DISP_LH(0xe3000000, 0x0004, BPF_REG_1, REG_0, REG_15, STK_OFF_SKBP);
Patches currently in stable-queue which might be from daniel@iogearbox.net are
queue-4.14/bpf-fix-integer-overflows.patch queue-4.14/bpf-fix-branch-pruning-logic.patch queue-4.14/bpf-s390x-do-not-reload-skb-pointers-in-non-skb-context.patch queue-4.14/bpf-sparc-fix-usage-of-wrong-reg-for-load_skb_regs-after-call.patch queue-4.14/bpf-fix-incorrect-tracking-of-register-size-truncation.patch queue-4.14/bpf-don-t-prune-branches-when-a-scalar-is-replaced-with-a-pointer.patch queue-4.14/bpf-verifier-fix-bounds-calculation-on-bpf_rsh.patch queue-4.14/selftests-bpf-add-tests-for-recent-bugfixes.patch queue-4.14/bpf-fix-corruption-on-concurrent-perf_event_output-calls.patch queue-4.14/bpf-fix-incorrect-sign-extension-in-check_alu_op.patch queue-4.14/bpf-ppc64-do-not-reload-skb-pointers-in-non-skb-context.patch queue-4.14/bpf-fix-missing-error-return-in-check_stack_boundary.patch queue-4.14/bpf-force-strict-alignment-checks-for-stack-pointers.patch queue-4.14/bpf-fix-32-bit-alu-op-verification.patch queue-4.14/bpf-fix-build-issues-on-um-due-to-mising-bpf_perf_event.h.patch