Patch "bpf: don't let ldimm64 leak map addresses on unprivileged" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

bpf: don't let ldimm64 leak map addresses on unprivileged

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
bpf-don-t-let-ldimm64-leak-map-addresses-on-unprivileged.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Daniel Borkmann <[email protected]>
Date: Mon, 8 May 2017 00:04:09 +0200
Subject: bpf: don't let ldimm64 leak map addresses on unprivileged

From: Daniel Borkmann <[email protected]>

[ Upstream commit 0d0e57697f162da4aa218b5feafe614fb666db07 ]

The patch fixes two things at once:

1) It checks the env->allow_ptr_leaks and only prints the map address to the log if we have the privileges to do so, otherwise it just dumps 0 as we would when kptr_restrict is enabled on %pK. Given the latter is off by default and not every distro sets it, I don't want to rely on this, hence the 0 by default for unprivileged.

2) Printing of ldimm64 in the verifier log is currently broken in that we don't print the full immediate, but only the 32 bit part of the first insn part for ldimm64. Thus, fix this up as well; it's okay to access, since we verified all ldimm64 earlier already (including just constants) through replace_map_fd_with_map_ptr().

---
 kernel/bpf/verifier.c |   21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

@@ -296,7 +296,8 @@ static const char *const bpf_jmp_string[
 	[BPF_EXIT >> 4] = "exit",
 };
 
-static void print_bpf_insn(struct bpf_insn *insn)
+static void print_bpf_insn(const struct bpf_verifier_env *env,
+			   const struct bpf_insn *insn)
 {
 	u8 class = BPF_CLASS(insn->code);
 

@@ -360,9 +361,19 @@ static void print_bpf_insn(struct bpf_in
 				insn->code,
 				bpf_ldst_string[BPF_SIZE(insn->code) >> 3],
 				insn->src_reg, insn->imm);
-		} else if (BPF_MODE(insn->code) == BPF_IMM) {
-			verbose("(%02x) r%d = 0x%x\n",
-				insn->code, insn->dst_reg, insn->imm);
+		} else if (BPF_MODE(insn->code) == BPF_IMM &&
+			   BPF_SIZE(insn->code) == BPF_DW) {
+			/* At this point, we already made sure that the second
+			 * part of the ldimm64 insn is accessible.
+			 */
+			u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
+			bool map_ptr = insn->src_reg == BPF_PSEUDO_MAP_FD;
+
+			if (map_ptr && !env->allow_ptr_leaks)
+				imm = 0;
+
+			verbose("(%02x) r%d = 0x%llx\n", insn->code,
+				insn->dst_reg, (unsigned long long)imm);
 		} else {
 			verbose("BUG_ld_%02x\n", insn->code);
 			return;

@@ -2704,7 +2715,7 @@ static int do_check(struct bpf_verifier_
 
 		if (log_level) {
 			verbose("%d: ", insn_idx);
-			print_bpf_insn(insn);
+			print_bpf_insn(env, insn);
 		}
 
 		err = ext_analyzer_insn_hook(env, insn_idx, prev_insn_idx);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/bpf-arm64-fix-jit-branch-offset-related-to-ldimm64.patch queue-4.10/bpf-don-t-let-ldimm64-leak-map-addresses-on-unprivileged.patch queue-4.10/bpf-enhance-verifier-to-understand-stack-pointer-arithmetic.patch