diff mbox series

[4.14,13/15] bpf/verifier: disallow pointer subtraction

Message ID 20210501043014.33300-14-fllinden@amazon.com
State New
Headers show
Series fix backports, add CVE-2021-29155 fixes | expand

Commit Message

Frank van der Linden May 1, 2021, 4:30 a.m. UTC 
From: Alexei Starovoitov <ast@kernel.org>

Upstream commit dd066823db2ac4e22f721ec85190817b58059a54

Subtraction of pointers was accidentally allowed for unpriv programs
by commit 82abbf8d2fc4. Revert that part of commit.

Fixes: 82abbf8d2fc4 ("bpf: do not allow root to mangle valid pointers")
Reported-by: Jann Horn <jannh@google.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
[fllinden@amazon.com: backport to 4.14]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
---
 kernel/bpf/verifier.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8ef1c74eaa11..abf85414c8d1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2754,7 +2754,7 @@  static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				 * an arbitrary scalar. Disallow all math except
 				 * pointer subtraction
 				 */
-				if (opcode == BPF_SUB){
+				if (opcode == BPF_SUB && env->allow_ptr_leaks) {
 					mark_reg_unknown(regs, insn->dst_reg);
 					return 0;
 				}