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authorAwais Belal <awais_belal@mentor.com>2018-05-10 14:12:22 +0500
committerAwais Belal <awais_belal@mentor.com>2018-05-10 14:37:34 +0500
commite5c5c71d216971220499a44de3f51c091f1ac049 (patch)
treebc74d0e18805385faed29f765b08b2a0e6b3f1f7 /common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch
parentdd06f966521a022d5ca7365859a9e0151b6945d0 (diff)
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linux-yocto/4.9: fix bpf backports for spectre/meltdown
A commit was missed during backports which generates failure during build. This now picks that commit up as well and updates the series appropriately. Signed-off-by: Awais Belal <awais_belal@mentor.com>
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch')
-rw-r--r--common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch83
1 files changed, 83 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch
new file mode 100644
index 00000000..fc0cb2fc
--- /dev/null
+++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0095-bpf-prevent-leaking-pointer-via-xadd-on-unpriviledge.patch
@@ -0,0 +1,83 @@
+From c7d695dd43368b0231ed509066131696d1533738 Mon Sep 17 00:00:00 2001
+From: Daniel Borkmann <daniel@iogearbox.net>
+Date: Thu, 29 Jun 2017 03:04:59 +0200
+Subject: [PATCH 095/103] bpf: prevent leaking pointer via xadd on
+ unpriviledged
+
+commit 6bdf6abc56b53103324dfd270a86580306e1a232 upstream.
+
+Leaking kernel addresses on unpriviledged is generally disallowed,
+for example, verifier rejects the following:
+
+ 0: (b7) r0 = 0
+ 1: (18) r2 = 0xffff897e82304400
+ 3: (7b) *(u64 *)(r1 +48) = r2
+ R2 leaks addr into ctx
+
+Doing pointer arithmetic on them is also forbidden, so that they
+don't turn into unknown value and then get leaked out. However,
+there's xadd as a special case, where we don't check the src reg
+for being a pointer register, e.g. the following will pass:
+
+ 0: (b7) r0 = 0
+ 1: (7b) *(u64 *)(r1 +48) = r0
+ 2: (18) r2 = 0xffff897e82304400 ; map
+ 4: (db) lock *(u64 *)(r1 +48) += r2
+ 5: (95) exit
+
+We could store the pointer into skb->cb, loose the type context,
+and then read it out from there again to leak it eventually out
+of a map value. Or more easily in a different variant, too:
+
+ 0: (bf) r6 = r1
+ 1: (7a) *(u64 *)(r10 -8) = 0
+ 2: (bf) r2 = r10
+ 3: (07) r2 += -8
+ 4: (18) r1 = 0x0
+ 6: (85) call bpf_map_lookup_elem#1
+ 7: (15) if r0 == 0x0 goto pc+3
+ R0=map_value(ks=8,vs=8,id=0),min_value=0,max_value=0 R6=ctx R10=fp
+ 8: (b7) r3 = 0
+ 9: (7b) *(u64 *)(r0 +0) = r3
+ 10: (db) lock *(u64 *)(r0 +0) += r6
+ 11: (b7) r0 = 0
+ 12: (95) exit
+
+ from 7 to 11: R0=inv,min_value=0,max_value=0 R6=ctx R10=fp
+ 11: (b7) r0 = 0
+ 12: (95) exit
+
+Prevent this by checking xadd src reg for pointer types. Also
+add a couple of test cases related to this.
+
+Fixes: 1be7f75d1668 ("bpf: enable non-root eBPF programs")
+Fixes: 17a5267067f3 ("bpf: verifier (add verifier core)")
+Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
+Acked-by: Alexei Starovoitov <ast@kernel.org>
+Acked-by: Martin KaFai Lau <kafai@fb.com>
+Acked-by: Edward Cree <ecree@solarflare.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ kernel/bpf/verifier.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
+index bfafb53..6767670 100644
+--- a/kernel/bpf/verifier.c
++++ b/kernel/bpf/verifier.c
+@@ -880,6 +880,11 @@ static int check_xadd(struct bpf_verifier_env *env, struct bpf_insn *insn)
+ if (err)
+ return err;
+
++ if (is_pointer_value(env, insn->src_reg)) {
++ verbose("R%d leaks addr into mem\n", insn->src_reg);
++ return -EACCES;
++ }
++
+ /* check whether atomic_add can read the memory */
+ err = check_mem_access(env, insn->dst_reg, insn->off,
+ BPF_SIZE(insn->code), BPF_READ, -1);
+--
+2.7.4
+