lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Wed, 3 Apr 2019 15:15:20 -0700
From:   Andrey Ignatov <rdna@...com>
To:     <netdev@...r.kernel.org>
CC:     Andrey Ignatov <rdna@...com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <kernel-team@...com>
Subject: [PATCH v2 bpf-next 1/5] bpf: Reject indirect var_off stack access in raw mode

It's hard to guarantee that whole memory is marked as initialized on
helper return if uninitialized stack is accessed with variable offset
since specific bounds are unknown to verifier. This may cause
uninitialized stack leaking.

Reject such an access in check_stack_boundary to prevent possible
leaking.

There are no known use-cases for indirect uninitialized stack access
with variable offset so it shouldn't break anything.

Fixes: 2011fccfb61b ("bpf: Support variable offset stack access from helpers")
Reported-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Andrey Ignatov <rdna@...com>
---
 kernel/bpf/verifier.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b7a7a9caa82f..88a0c6e0b5a8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2213,6 +2213,15 @@ static int check_stack_boundary(struct bpf_verifier_env *env, int regno,
 		if (err)
 			return err;
 	} else {
+		/* Only initialized buffer on stack is allowed to be accessed
+		 * with variable offset. With uninitialized buffer it's hard to
+		 * guarantee that whole memory is marked as initialized on
+		 * helper return since specific bounds are unknown what may
+		 * cause uninitialized stack leaking.
+		 */
+		if (meta && meta->raw_mode)
+			meta = NULL;
+
 		min_off = reg->smin_value + reg->off;
 		max_off = reg->umax_value + reg->off;
 		err = __check_stack_boundary(env, regno, min_off, access_size,
-- 
2.17.1

Powered by blists - more mailing lists