summaryrefslogtreecommitdiffstats
path: root/net
diff options
context:
space:
mode:
authorDaniel Borkmann <daniel@iogearbox.net>2020-09-08 00:04:10 +0200
committerAlexei Starovoitov <ast@kernel.org>2020-09-08 18:16:12 +0200
commite6a18d36118bea3bf497c9df4d9988b6df120689 (patch)
tree64f7a4cadc744126fbbb70f568426f785a570c9a /net
parentMerge branch 'hashmap_iter_bucket_lock_fix' (diff)
downloadlinux-e6a18d36118bea3bf497c9df4d9988b6df120689.tar.xz
linux-e6a18d36118bea3bf497c9df4d9988b6df120689.zip
bpf: Fix clobbering of r2 in bpf_gen_ld_abs
Bryce reported that he saw the following with: 0: r6 = r1 1: r1 = 12 2: r0 = *(u16 *)skb[r1] The xlated sequence was incorrectly clobbering r2 with pointer value of r6 ... 0: (bf) r6 = r1 1: (b7) r1 = 12 2: (bf) r1 = r6 3: (bf) r2 = r1 4: (85) call bpf_skb_load_helper_16_no_cache#7692160 ... and hence call to the load helper never succeeded given the offset was too high. Fix it by reordering the load of r6 to r1. Other than that the insn has similar calling convention than BPF helpers, that is, r0 - r5 are scratch regs, so nothing else affected after the insn. Fixes: e0cea7ce988c ("bpf: implement ld_abs/ld_ind in native bpf") Reported-by: Bryce Kahle <bryce.kahle@datadoghq.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/cace836e4d07bb63b1a53e49c5dfb238a040c298.1599512096.git.daniel@iogearbox.net
Diffstat (limited to 'net')
-rw-r--r--net/core/filter.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index b2df52086445..2d62c25e0395 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7065,8 +7065,6 @@ static int bpf_gen_ld_abs(const struct bpf_insn *orig,
bool indirect = BPF_MODE(orig->code) == BPF_IND;
struct bpf_insn *insn = insn_buf;
- /* We're guaranteed here that CTX is in R6. */
- *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_CTX);
if (!indirect) {
*insn++ = BPF_MOV64_IMM(BPF_REG_2, orig->imm);
} else {
@@ -7074,6 +7072,8 @@ static int bpf_gen_ld_abs(const struct bpf_insn *orig,
if (orig->imm)
*insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, orig->imm);
}
+ /* We're guaranteed here that CTX is in R6. */
+ *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_CTX);
switch (BPF_SIZE(orig->code)) {
case BPF_B: