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authorDaniel Borkmann <daniel@iogearbox.net>2019-04-03 18:39:10 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-04-20 09:15:09 +0200
commit17efa65350c5a251ba7d90a56abc65205a204a03 (patch)
tree3feb8c2fadba9f25daf17348247662999ed6cdd8 /kernel
parentba9d2e0cc870d1a16195c801aa18b33cd70125b9 (diff)
bpf: restrict unknown scalars of mixed signed bounds for unprivileged
commit 9d7eceede769f90b66cfa06ad5b357140d5141ed upstream. For unknown scalars of mixed signed bounds, meaning their smin_value is negative and their smax_value is positive, we need to reject arithmetic with pointer to map value. For unprivileged the goal is to mask every map pointer arithmetic and this cannot reliably be done when it is unknown at verification time whether the scalar value is negative or positive. Given this is a corner case, the likelihood of breaking should be very small. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> [backported to 4.14 sblbir] Signed-off-by: Balbir Singh <sblbir@amzn.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/verifier.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index bc073789b693..c4b81d15fbc2 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2014,8 +2014,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
+ u32 dst = insn->dst_reg, src = insn->src_reg;
u8 opcode = BPF_OP(insn->code);
- u32 dst = insn->dst_reg;
dst_reg = &regs[dst];
@@ -2189,6 +2189,13 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
verbose("R%d bitwise operator %s on pointer prohibited\n",
dst, bpf_alu_string[opcode >> 4]);
return -EACCES;
+ case PTR_TO_MAP_VALUE:
+ if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
+ verbose("R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
+ off_reg == dst_reg ? dst : src);
+ return -EACCES;
+ }
+ /* fall-through */
default:
/* other operators (e.g. MUL,LSH) produce non-pointer results */
if (!env->allow_ptr_leaks)